Failure of normal Leydig cell development in follicle-stimulating hormone (FSH) receptor-deficient mice,but not FSHbeta-deficient mice: role for constitutive FSH receptor activity

Previous studies have suggested that FSH may be involved in regulation of Leydig cell function. We have examined this directly using two mouse models with null mutations in either the FSH beta-subunit (FSHbetaKO mice) or the FSH receptor (FSHRKO mice). Circulating LH levels were normal in adult FSHbetaKO mice, but were significantly increased in FSHRKO mice. Intratesticular testosterone levels increased normally in FSHbetaKO mice from birth to adulthood, whereas testosterone levels in FSHRKO mice failed to increase normally after puberty and were significantly reduced in adult animals. This was associated with reduced levels of mRNA encoding cytochrome P450 side-chain cleavage, 3beta-hydroxysteroid dehydrogenase type VI, and steroidogenic acute regulatory protein in FSHRKO mice. Leydig cell number was normal in FSHbetaKO mice during development, but in FSHRKO mice Leydig cell number increased slowly after puberty and was significantly reduced in the adult animal. Transfection studies showed that the FSHR exhibits constitutive activity in the absence of agonist stimulation. The results indicate, therefore, that Sertoli cells regulate the development of Leydig cell number and that constitutive activity within the FSHR is sufficient to stimulate this process. The presence of the hormone itself is not required when circulating LH levels are adequate.     

Effects of the gonadotrophin-releasing hormone agonist 'Zoladex' upon pituitary and gonadal function in hypogonadal (hpg) male mice: a comparison with normal male and testicular feminized (tfm) mice.

Hypogonadal (hpg) mutant mice, with a congenital deficiency of hypothalamic gonadotrophin-releasing hormone (GnRH), and testicular feminized (tfm) mice, which lack a functional androgen receptor, were used to study the effects of the potent GnRH agonist 'Zoladex' (ICI 118630; D-Ser (Bu(t))6, Azgly10-GnRH) on pituitary and gonadal function. Zoladex (0.5 mg) in a sustained-release lactide-glycolide copolymer depot was administered subcutaneously under anaesthesia and was left in place for 7 days, after which time the effects of the drug upon pituitary and serum gonadotrophin concentrations, glycoprotein hormone subunit mRNAs and testicular morphology were investigated. At the pituitary level, Zoladex treatment resulted in a substantial reduction in LH content in normal males, and LH content was depressed in hpg mice even below the basal levels normally found in these mutants. Pituitary LH content in the Zoladex-treated animals was depressed in the tfm groups, but not to the same levels as those found in the normal and castrated normal mice. Zoladex treatment at the time of castration prevented the post-operative elevation in serum LH associated with castration alone. In the androgen-deficient tfm mouse, Zoladex did not depress the normally elevated serum LH levels. Serum LH in the hpg animals was, in all cases, below the limit of detection of the assay. Pituitary FSH content was depressed into the hpg range in both the normal and castrated animals, but there was no further depression in the hpg mice. The pituitary content was reduced in the tfm mice, again the effects not being as dramatic as in the normal and castrated animals. Serum FSH content, as measured by radioimmunoassay, was depressed by 50% in normal mice; there was no reduction in the hpg mice, however. With regard to pituitary gonadotrophic hormone gene expression, Zoladex administration to normal mice caused a dramatic reduction in LH beta mRNA content, to a level approximating that found in untreated hpg mice. The drug also depressed LH beta mRNA in the castrated group to the hpg range when given at the time of castration, whereas in untreated castrated mice there was a significant increase in LH beta mRNA. In the tfm mouse, which can be considered as a model for long-term failure of androgen feedback, Zoladex again induced a fall in LH beta mRNA, but not to the same extent as in the normal and normal castrated group. Zoladex had no effect on the already low levels of LH beta mRNA found in hpg mice.(ABSTRACT TRUNCATED AT 400 WORDS)     

Impaired regulation of gonadotropins leads to the atrophy of the female reproductive system in klotho-deficient mice

klotho-Deficient mice exhibit a syndrome resembling human premature ageing, with multiple pathological phenotypes in tissues including reproductive organs. It was proposed that Klotho might possess the hormonal effects on many organs. In this study, the female reproductive system of klotho mice was examined to reveal the mechanism that brought the female sterility by histological and molecular approaches. We observed cessation of ovarian follicular maturation at the preantral stage and the presence of numerous atretic ovarian follicles and atrophic uteri. In situ hybridization analysis revealed that LH receptor and aromatase P450 were not expressed in the ovaries. These results suggest the impairment of gonadal development during the antral transition process. We next addressed the responsible organs for the failure of antral transition. Transplantation of klotho ovaries to wild-type mice resulted in the ability to bear offspring. Administration of FSH or GnRH induced advanced maturation of ovaries and uteri in klotho mice. These results indicate that the female reproductive organs in klotho mice are potentially functional and that klotho gene deficiency leads to the atrophy of reproductive organs via impairment of the hypothalamic-pituitary axis. Absence of the estrus cycle and constant low trends of both FSH and LH levels were found in female klotho mice. Immunohistochemical analysis revealed that the production of both FSH and LH were decreased in pituitary gland. Taken together, our findings suggest the involvement of klotho in the regulatory control of pituitary hormones.     

Effects of bovine follicular fluid on gonadotrophin secretion in intact and chronically ovariectomized ewes before and after desensitization of pituitary gonadotrophs to gonadotrophin-releasing hormone

Intact and chronically ovariectomized ewes were treated for 4 days with charcoal-treated bovine follicular fluid (FF) or charcoal-treated bovine serum during the late-anoestrous period, and the effects on basal and gonadotrophin-releasing hormone (GnRH)-induced secretion of LH and FSH observed. Subsequently, ewes received s.c. implants containing a sustained-release formulation of a potent GnRH agonist D-Ser(But)6-Azgly10-LHRH (ICI 118630) to desensitize pituitary gonadotrophs to hypothalamic stimulation, and the effects of bovine FF and bovine serum were re-assessed 2 weeks later. Chronic exposure (for 2-3 weeks) to ICI 118630 significantly reduced basal levels of LH and FSH in both intact and ovariectomized ewes and completely abolished both spontaneous LH pulses as well as exogenous GnRH-induced acute increases in plasma LH and FSH levels. Treatment with bovine FF significantly reduced plasma FSH levels, but not LH levels, in both intact and ovariectomized ewes before and after chronic exposure to ICI 118630. In intact ewes before exposure to ICI 118630, treatment with bovine FF actually enhanced pulsatile LH secretion and raised mean plasma LH levels by 240% (P less than 0.05). No such stimulatory effect of bovine FF on LH secretion was observed in intact ewes exposed to ICI 118630 or in ovariectomized ewes before or after exposure to ICI 118630, suggesting that the effect probably involved an alteration in ovarian steroid feedback affecting hypothalamic GnRH output. Treatment with bovine FF did not significantly affect the magnitude of GnRH-induced surges of LH or of FSH observed in either intact or ovariectomized ewes before exposure to ICI 118630.(ABSTRACT TRUNCATED AT 250 WORDS)     

Luteinizing hormone promotes gonadal tumorigenesis in inhibin-deficient mice

The inhibins are secreted alpha:beta heterodimers of the TGF-beta superfamily that are mainly synthesized in Sertoli cells and granulosa cells, and are critical regulators of testicular and ovarian development and function. Mice homozygous for a targeted deletion of the inhibin alpha subunit gene (Inha(-/-)) develop sex cord-stromal tumors in a gonadotropin-dependent manner. Here, we determine the contribution of LH to gonadal tumorigenesis by generating mice deficient in both inhibins and LH. Inha(-/-)Lhb(-/-) mice have increased survival and delayed tumor progression, and these observations correlate with lower serum FSH and estradiol levels compared to Inha(-/-) controls. Double mutant testicular tumors demonstrate decreased expression of cyclin D2, while double mutant ovarian tumors have elevated expression of p15(INK4b) and trend toward higher levels of p27(Kip1). We conclude that LH is not required for tumor formation in the absence of inhibins but promotes tumor progression, likely through alterations in serum hormone levels and cell cycle regulators.     

SERUM LUTEINIZING HORMONE AND FOLLICLE STIMULATING HORMONE IN NORMAL CHILDREN AND PATIENTS WITH VARIOUS CLINICAL DISORDERS

Serum concentrations of luteinizing hormone (LH) and follicle stimulating hormone (FSH) were determined in 329 normal children and 185 individuals with endocrinological abnormalities or variations of development. A significant increase of gonadotrophins is noted at the onset of puberty among the boys and at menarche for girls. The values are compared with serum concentrations of LH and FSH in children with abnormalities of sexual development, pituitary malfunction as well as other clinical abnormalities. Comparable levels for age and stage of development were found for premature thelarche, premature adrenarche, cryptorchidism, male pseudohermaphroditism and pubertal gynaecomastia. Hypogonadal individuals (Klinefelter's and Turner's syndrome, pure ovarian dysgenesis and testicular dysgenesis) have markedly elevated values while those with pituitary hypofunction had low values. Patients with sexual prococity tended to have elevated concentrations.     

FSH, LH and prolactin levels, ovarian follicular development and ovarian responsiveness to FSH in the Snell dwarf mouse

The homozygous Snell dwarf mouse is sterile. It has been shown that pituitary hormone levels are low in 3 month old animals except for FSH and LH whose pituitary contents and plasma concentrations are normal. In this study, the pituitary FSH, LH and prolactin (Prl) content, the FSH plasma concentration and the ovarian follicular development of the Snell dwarf mouse were studied at 18, 20, 24, 40 and 80 days of age. Normal mice were also studied at the same age and served as controls. Pituitary FSH was significantly lower in dwarf mice compared with controls during the period days 18 to 30, while plasma FSH was significantly lower during the period days 20 to 80. Pituitary LH was significantly lower in dwarf mice during the period days 18 to 40. In normal mice, pituitary Prl increased with age, but remained consistently low in dwarf mice. The normal number of growing follicles was similar in dwarf mice and controls up to day 30, but thereafter the total number of growing follicles was greater in the controls. In the dwarf mice, the production of antral follicles was low and there were no ovulations. The rates of atresia were similar in the two genotypes. The responsiveness of the dwarf mouse ovary to FSH was then examined. When dwarf and control mice were supplemented with FSH for 5 days starting at 24 days of age, the ovarian and uterine weights increase 6- and 5-fold, respectively, in the dwarf mice, and 2- to 3-fold in the normal mice.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pituitary gonadotropin-releasing hormone receptor regulation in mice. II: Females

The regulation of pituitary GnRH receptors (GnRH-R) by gonadal steroids was examined in female mice housed in a constant environment (six to 8 per cage in same room as males). A 60% decrease in GnRH-R occurred 7 days after ovariectomy (OVX) (9.2 +/- 0.9 fmol/pituitary OVX vs. 25 +/- 2 for intact random estrous cycle controls). The receptor affinity (Ka 1.86 X 10(9) M-1) remained constant in intact and OVX female mouse pituitary particles. The pattern of GnRH-R fall after OVX was similar to that found in male mice, except that the GnRH-R decrease began some 6 h later than in males and serum LH also rose more slowly. Serum FSH was significantly elevated 6 h post OVX. In contrast to males, pituitary LH, in spite of a rapid fall (60%) at 12 h, regained the random, estrous cycle control value by 4 days post OVX and then increased to above this level. Pituitary FSH, unlike in males, remained at the intact value (3.1 +/- 0.24 micrograms/pituitary) up to 24 h post OVX and then gradually rose to 7.9 +/- 0.37 micrograms/pituitary on day 4 and 15.5 +/- 0.32 micrograms/pituitary on day 7. Treatment of OVX female mice with estradiol-17 beta (300 ng/day) attenuated the postcastration GnRH-R fall, and was more effective when combined with progesterone (375 micrograms/day). Progesterone alone was ineffective. The GnRH-R fall post OVX persisted for up to 2 months, despite elevated serum and pituitary LH and FSH levels. GnRH-R fell by 40% in lactating mice (20.6 +/- 0.95-lactating vs. 32.4 +/- 1.25 fmol/pituitary-random, estrous cycling females). Serum LH was reduced by 70% in lactating mice. These findings are qualitatively and quantitatively similar to those in lactating rats suggesting that, in this physiological situation, a similar mechanism may account for the receptor fall in both species. In sex reversed (Sxr) mice (genotypic female-phenotypic male) GnRH-R values were about 50% higher than those of intact normal male and normal, random estrous cycling, female values. This was the only situation in mice in which pituitary GnRH-R increases were observed to date. Serum and pituitary LH and FSH values in Sxr mice were elevated, especially when compared with normal, random estrous cycling female controls. The results indicate that pituitary GnRH-R of female mice fall in response to removal of gonadal steroid feedback, in the same way as males.(ABSTRACT TRUNCATED AT 400 WORDS)     

Annual cycle of pituitary and plasma gonadotropins and plasma sex steroids in a wild population of the toad, Bufo japonicus

Pituitary and plasma gonadotropins and plasma sex steroids of free-living toads, Bufo japonicus, were measured monthly from March 1981 to February 1982 and examined in relation to gonadal cycles. Toads were captured at Mizuno, Saitama Prefecture. Individual blood samples were collected by cardiac puncture within 3 min of capture in the field. In males, testicular weight was maximal in August. Plasma follicle-stimulating hormone (FSH) levels changed in association with testicular weight. Plasma androgen levels showed a small peak in November and a large peak in March just prior to breeding. Plasma luteinizing hormone (LH) levels changed in parallel with plasma androgen levels. In females, neither plasma FSH nor LH alone were correlated significantly with ovarian weight. However, ovarian and oviductal weights both correlated significantly with plasma steroid levels. Plasma estradiol levels showed a sharp peak in March, followed by a rapid decrease to the minimum in April. A gradual increase of estradiol occurred from July to November in parallel with an increase in ovarian weight. Changes in plasma progesterone and androgen levels in females resembled those for estradiol. However, the changes in progesterone were not so marked as in estradiol. Plasma androgen levels in females were especially high between January and March. In both sexes, the pituitary gonadotropin contents changed in parallel with plasma levels of both FSH and LH. The pituitary almost always contained more LH than FSH, while the reverse was true in the plasma in both sexes. In addition, plasma FSH levels increased markedly in early summer when plasma LH remained unchanged (males) or increased only slightly (females). These results indicate that the toad may serve as excellent material for the study of differential control of FSH and LH secretion.     

The effect of naloxone on endogenous opioid regulation of pituitary gonadotropins and prolactin during the menstrual cycle

To determine the influence of ovarian sex steroid hormones on endogenous opioid regulation of pituitary FSH, LH, and PRL secretion, six women were studied during the follicular phase (days 8-9) and luteal phase (days 21-23) of their menstrual cycles. An iv bolus dose of 10 mg of the opiate antagonist naloxone was given, and plasma FSH, LH, and PRL were measured at -30, -15, 0, 15, 30, 45, 60, 90, 120, and 180 min. During the follicular phase, baseline plasma FSH and LH levels were 10.7 +/- 0.9 and 16.7 n+/- 2.0 mIU/ml (mean +/- SEM), respectively; the plasma PRL level was 11.7 +/- 1.2 ng/ml. Naloxone did not significantly alter plasma FSH, LH, or PRL during the follicular phase. Basal levels of LH were significantly lower during the luteal phase than during the follicular phase (P less than 0.01). During the luteal phase, plasma LH increased significantly from a basal level of 10.0 +/- 1.0 to 20.8 +/- 3.0 mIU at 30 min (P less than 0.001) and remained significantly elevated at 90 min. Similarly, plasma PRL increased significantly from a basal level of 11.0 +/- 0.7 to 16.2 +/- 2.7 ng/ml at 30 min (P less than 0.025), but decreased by 90 min to 12.5 +/- 1.5 ng/ml. Plasma FSH did not change after naloxone treatment. Our results suggest that endogenous opiates have a prominent inhibitory effect on pituitary gonadotropin and PRL secretion only during the luteal phase of the menstrual cycle.     

Effect of inhibin like factors on gonadotrophin release by the mouse pituitary in vitro

The release of gonadotrophins by the mouse whole pituitary in vitro was investigated. Whole tissue from 34 day old male mice was highly responsive to synthetic LRH in short incubations at 37 degrees C. About 15% of FSH and 17% of LH were secreted during a 3 h pulse with 3 ng of LRH. Pre-exposure of the mouse pituitary to fractions containing inhibin activity, inhibited the FSH release induced by LRH. Inhibin from bovine and human seminal plasma and porcine follicular fluid preferentially inhibited FSH secretion, while LH secretion was also reduced by inhibin like factors from bovine follicular fluid and testicular extract. The inhibition of FSH and/or LH release was measured by specific radioreceptor assays and could not be due to destruction of either gonadotrophin or LRH. Purified bovine seminal plasma inhibin was effective at very low concentrations in vitro. The whole incubation system is simple and an estimation of inhibition of bioactive (binding activity) FSH release can be obtained within 24 h.     

LH suppression following different low doses of the GnRH antagonist ganirelix in polycystic ovary syndrome

Elevated LH concentration is a common feature in polycystic ovary syndrome (PCOS). This study was designed to establish whether elevated LH levels in PCOS might be suppressed to normal range values by the administration of different low doses of GnRH antagonist, which subsequently might reverse the anovulatory status of these patients. Twenty-four PCOS patients with elevated endogenous LH concentrations were randomized into 3 different dose groups, receiving either 0.125 mg (Group A), 0.250 mg (Group B) or 0.500 mg (Group C) ganirelix sc daily for 7 subsequent days. During the first day of treatment, LH and FSH levels were assessed at 20 min intervals, during 8 h. Thereafter LH, FSH, androgens, estradiol (E2) and inhibins were assessed daily and frequent ultrasound scans were performed for 7 days to record follicle development. Repeated GnRH antagonist administration induced a significant suppression of LH (and to a lesser extent of FSH) serum levels, which was comparable between the different doses. Six hours after ganirelix administration, endogenous LH was suppressed by 49, 69 and 75%, and endogenous FSH was suppressed by 23, 19 and 25%, respectively. The decrease in serum LH and FSH levels was transient and lasted for 12 h, after which serum levels returned to baseline levels at 24 h after drug administration. Androgen levels were not significantly suppressed using this regimen. E2 levels decreased significantly (p < 0.001) and suppression was most pronounced in Group C. Spontaneous follicle development or ovulations were not recorded during the course of treatment. In conclusion, the present study demonstrates that the GnRH antagonist ganirelix is capable of normalising elevated LH levels in PCOS patients, in doses similar to the ones previously shown to prevent a premature LH rise during ovarian hyperstimulation for in vitro fertilization (IVF). In addition, the transient suppression of elevated endogenous LH levels per se does not re-establish normal follicle development in PCOS. However, follicle development may be insufficiently supported by the accompanied subtle suppression of endogenous FSH. Similarly, a transient decline in E2 levels does not effectively restore normal pituitary ovarian feedback. Moreover, these results support the contention of a limited role of LH in the pathogenesis of PCOS.     

Interrelationships between ovarian and pituitary hormones in ovulatory menstrual cycles across reproductive age

CONTEXT: Ovarian hormones regulate pituitary gonadotropin secretion across the menstrual cycle via negative and positive feedback mechanisms. The contribution of individual hormones is complex and is a continuing area of research. OBJECTIVE: The aim of the study was to identify relationships between LH/FSH and estradiol, progesterone, inhibin A, inhibin B, and anti-Mullerian hormone (AMH) in ovulatory menstrual cycles across reproductive age. DESIGN: Serum ovarian and pituitary hormones were studied in a group of young (<35 yr; n = 21) and older (>45 yr; n = 55) women. The slopes of the regression lines relating the ovarian and pituitary hormones were determined by multiple linear regression analysis and expressed with 95% confidence intervals for each ovarian hormone, with FSH and LH as independent variables. Both simultaneous and delayed (time lagged) relationships were examined. RESULTS: Clear associations were evident for the lagged prediction of FSH, with significant negative associations being evident with inhibin B and AMH in the follicular phase and with estradiol, inhibin B, progesterone, and AMH in the luteal phase. For the lagged prediction of LH, significant positive and negative associations were observed with estradiol and inhibin B, respectively, in the follicular phase and a negative association with progesterone and inhibin B in the luteal phase. CONCLUSIONS: It is concluded that in the follicular phase, inhibin B is a major feedback regulator of FSH and may also be a negative feedback regulator of LH. AMH may be indirectly involved in FSH regulation.     

Common melanocortin-3 receptor variants are not associated with obesity, although rs3746619 does influence weight in obese individuals

Clinically non-functional pituitary adenomas are often derived from gonadotropin producing cells. However, gonadotropinomas causing elevated serum levels of follicle-stimulating hormone (FSH) and clinical signs of FSH hypersecretion are very rarely described. Our patient, a 56-year-old man, was referred to our clinic with signs of hypogonadism. Magnetic resonance imaging (MRI) and biochemical examinations showed a large pituitary adenoma and excessive levels of serum FSH. Clinical examination and ultrasound measurement revealed bilaterally enlarged testes. After pituitary surgery, serum FSH levels normalized and there was a decrease in testicular volume. This case suggests that supraphysiological levels of FSH from a gonadotropinoma can cause a clinically observable effect, i.e. testicular enlargement. This is in line with experimental studies showing biological effect of FSH from pituitary adenomas and previous occasional reports of ovarian hyperstimulation and testicular enlargement in patients with FSH-secreting gonadotropinomas.     

TESTICULAR ENLARGEMENT AND ELEVATED SERUM INHIBIN CONCENTRATIONS OCCUR IN PATIENTS WITH PITUITARY MACROADENOMAS SECRETING FOLLICLE STIMULATING HORMONE

We studied four male patients with pituitary macroadenomas. Before treatment all had high serum FSH concentrations, but LH and testosterone were normal or subnormal; all patients were found to have large testes. All had had normal sexual function, and three patients had fathered children. After pituitary surgery there were decreases in serum gonadotrophins and testosterone, which were accompanied by decreases in testicular volumes. hCG stimulation tests in two patients showed normal responses of testosterone and oestradiol, confirming normal Leydig cell function. Inhibin levels were increased in two patients studied when FSH levels were high, suggesting a defect in gonadal-pituitary feedback control. Later, as FSH concentrations decreased to normal, so did inhibin levels. Histology showed that increased testicular size was due to increased lengths of seminiferous tubules. The association of pituitary macroadenomas, large testes and increased serum inhibin has not been reported previously. Assessment of testicular size in patients with raised serum FSH is important, since enlarged testes suggest the likely pathogenesis is that of a pituitary gonadotrophinoma, rather than primary gonadal failure. Increased inhibin levels may then confirm this, and be a biochemical marker for these tumours.     

The impact of ovarian laser surgery on the gonadotrophin secretion in women with polycystic ovarian disease

To evaluate the effects of ovarian surgery on the deranged episodic gonadotrophin release of women with the polycystic ovarian disease (PCOD), we studied 11 patients with the clinical and endocrinological features of PCOD before and after laparoscopic laser coagulations of ovarian surfaces and cysts. During both occasions, blood was collected at 15-min intervals for 8 h to determine LH and FSH secretory profiles and additionally for 3 h during GnRH injections (25 micrograms twice within 2 h) to assess pituitary responsiveness. Serum testosterone, androstendione and oestrogen (oestrone, oestradiol) levels were markedly reduced (P less than 0.05 or less) after surgery. Mean LH concentrations declined (P less than 0.001), while FSH levels increased (P less than 0.01) following laser treatments. The LH pulse frequencies (by Cluster analysis) did not change after ovarian surgery, but the LH pulse amplitudes were markedly reduced (P less than 0.01). Lower (P less than 0.05 or less) LH concentrations were attained in response to GnRH challenges, and the stimulated FSH release also tended to decrease after laser treatments. Thus, ovarian surgery in PCOD women resulted in reduced serum sex steroid concentrations and in divergent effects on serum LH and FSH levels. The attenuated pituitary LH responsiveness after ovarian surgery suggests action of sex steroids primarily at the pituitary site, while the increase in FSH concentrations may be attributed to other factors selectively modulating FSH release.     

Lack of vasoactive intestinal peptide reduces testosterone levels and reproductive aging in mouse testis

The neuropeptides vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide have long been considered as putative regulators of testicular functions. In vitro evidence suggests that VIP could play an important role in testosterone biosynthesis. However, the endogenous role of VIP on testicular functions remained to be demonstrated. In C57BL/6 mice exhibiting a complete disruption of the VIP gene, we first observed here that serum testosterone levels were lower than those of WT littermates. At the age of 4 months, this phenotype was accompanied with a reduction of expression of StAR and 3-beta-hydroxysteroid dehydrogenase (3beta-HSD) in the testis. In addition, serum levels of FSH but not LH were reduced in young knock-out (KO) males. Testicular anatomy also revealed a higher percentage of degenerated seminiferous tubules in the 4-month-old VIP KO animals when compared with WT. In 15-month-old animals, control males showed typical testicular aging, including a severe degeneration of seminiferous tubules, a dramatic decrease in serum levels of testosterone, and a reduction in StAR and 3beta-HSD gene expression. In age-matching VIP KO males, the levels of serum testosterone and steroidogenic enzymes were still very low. Interestingly, in contrast to that observed in young mice, testicular degeneration at 15 months was significantly less severe in VIP KO than WT mice. All together, these results suggest that 1) VIP is an important factor for regulating testosterone biosynthesis and FSH secretion and 2) VIP may influence testicular aging.     

A quantitative analysis of the maturation of steroid negative feedbacks controlling gonadotropin release in the female rat: the infantile-juvenile periods, transition from an androgenic to a predominantly estrogenic control

To determine what ovarian or adrenal steroid(s) are involved in restraining gonadotropin secretion in infantile female rats, several experiments were performed. Adrenalectomy of 10-day-old rats markedly decreased serum progesterone (P) and, to a lesser extent, serum estradiol (E2) levels. Androgen (A) levels were only transiently reduced, and serum dihydrotestosterone was not affected. Serum LH and FSH, on the other hand, increased only transiently after adrenalectomy. Ovariectomy (OVX) failed to decrease serum P and partially depressed serum E2, but resulted in a marked fall of both testosterone (T) and dihydrotestosterone. Serum LH and FSH were increased in these animals. Replacement of pre-OVX serum T levels via Silastic capsules prevented the postcastration rise in both LH and FSH, suggesting that the increase in gonadotropins that follows OVX of 10-day-old rats is, to a large extent, a consequence of the loss of ovarian T. OVX of juvenile (27 days old) rats increased serum FSH and LH 48 h later and reduced both serum T and E2 levels, with no significant change in serum P. Replacement of pre-OVX serum T levels depressed post-OVX serum FSH and LH titers only partially. In contrast, replacement of pre-OVX serum E2 levels, effectively suppressed the postcastration rise in serum gonadotropins. The results suggest that 1) during the infantile period, gonadotropin release is predominantly under ovarian androgenic inhibitory control, but this mechanism is not very effective, because basal serum gonadotropin levels, particularly FSH, are elevated; 2) the effectiveness of the A negative feedback on FSH remains unchanged during prepubertal development; and 3) the previously reported increase in E2 negative feedback effectiveness that occurs after day 15 results in an E2 inhibitory signal that surpasses that of As, so that during juvenile days, most of the ovarian steroidal inhibitory control on gonadotropin release is mediated by E2.     

HYPOTHALAMIC-PITUITARY-OVARIAN FUNCTION IN PERIMENOPAUSAL WOMEN

In a group of nine perimenopausal women, aged 37–52 years, with dynsfunctional uterine bleeding (DUB), serial measurements were made of urinary total oestrogen and pregnanediol excretion and of plasma gonadotrophin and steroid levels under basal conditions and during dynamic tests (oestrogen provocation and LHRH-tests). Results were compared to those obtained in a control group of regularly menstruating women, 23–45 years of age. Four different patterns of hypothalamic-pituitary-ovarian (H.P.O.) activity were identified in the perimenopausal subjects with DUB. In two patients with a history of persistent anovulation and cystic glandular hyperplasia of the endometrium, basal plasma gonadotrophin levels were normal but there was a failure to release an adequate amount of LH in response to endogenous and exogenous oestrogen stimulation. One subject had regular ovulatory cycles but the follicular phase was shorter and circulating levels of FSH, but not of LH, were higher than in controls. A similar monotropic increase in FSH was also present in a further patient whose cycles were irregular and included an ovulatory cycle with short follicular phase, an ovulatory cycle of normal length and an anovulatory cycle. In the remaining five women follicular development was infrequent and anovulation the rule. FSH and LH levels in these women were elevated despite the presence of circulating 17β-oestradiol levels in the early-mid follicular phase range. At the time of menopausal transition in one of these subjects, the decline of plasma 17β-oestradiol to undetectable levels was associated with a further rise of both gonadotrophins. Conversely, following a prolonged period of follicular development with elevated urinary total oestrogen excretion in another subject, the raised gonadotrophin concentrations were suppressed and the pituitary response to LHRH was within the normal range. LHRH responses in the other four women were augmented. Oestrogen administration failed to induce a normal LH surge in three out of the five subjects. The results indicate that marked changes in the pattern of pituitary gonadotrophin secretion can be found in perimenopausal women with DUB. The observed increase in peripheral levels of FSH (with or without concomitant increase in LH) may be due to a change in hypothalamic-pituitary sensitivity to the feedback effects of oestrogen. Alternatively, it is possible that these changes result from a decrease in the ovarian secretion of a hypothetical ‘inhibin-like' substance produced by the growing follicle and for which the name ‘FSH-release inhibiting substance’ (‘FRIS’) is proposed.     

SEX HORMONE LEVELS AND GONADOTROPHIN RELEASE IN THE POLYCYSTIC OVARY SYNDROME

The response to synthetic luteinizing hormone-releasing hormone was studied in eighteen patients with the polycystic ovary syndrome. The release of follicle-stimulating hormone was similar to that found in normal women. The mean response of luteinizing hormone was similar to that found in the luteal phase, but significantly greater (P<0.02) than that found in the early follicular phase of the normal menstrual cycle. Basal serum levels of FSH and LH, estimated in twenty-five patients, were similar to those found in normal subjects. The sex hormone binding globulin capacity was reduced in twenty-four of them. Basal serum testosterone levels were elevated in twelve of twenty-two patients and the mean level was significantly greater (P<0.01) than the mean level of normal women. Basal serum androstenedione levels were elevated in nine of twenty-two patients and the mean level was also significantly greater (P<0.02) than normal. There was a highly significant negative correlation (r=?0.86; P<0.001) between basal testosterone and LH levels. These data suggest that the pituitary gland of patients with the polycystic ovary syndrome contains adequate amounts of LH but that the ovulatory surge of LH which occurs in normal women is inhibited by testosterone acting on either the pituitary or, more probably, on the hypothalamus.