Effects of an early postnatal treatment of hypogonadotropic hypogonadism with a continuous subcutaneous infusion of recombinant follicle-stimulating hormone and luteinizing hormone

BACKGROUND: The neonatal-midinfancy surge in pulsatile gonadotropin secretion is attributable to an increase in GnRH pulse amplitude and is associated with a rapid expansion of Leydig and Sertoli cell populations with concomitant surges in testosterone, inhibin, and anti-Mullerian hormone production as well as an increase in testicular volume. Boys with congenital hypogonadotropic hypogonadism (HH) do not activate these processes. A potential cause for azoospermia and infertility in adult life is deficient proliferation of immature Sertoli cells before and during puberty due to the absence of FSH. OBJECTIVE: The objective of the study was to investigate whether early postnatal continuous sc infusion of gonadotropins could mimic the physiological growth of testes and to evaluate responses of the Leydig and Sertoli cells to early gonadotropin replacement. DESIGN AND METHODS: Two neonates (P1 with hypotuitarism and P2 with HH) with micropenis and microorchidism were treated for 6 months with high doses of recombinant LH and FSH (a gift of Luveris and Gonal-F from Serono, Lyon, France) delivered sc with an insulin pump. RESULTS: Gonadotropin continuous sc infusion increased mean serum LH and FSH to normal or supranormal levels. Mean testosterone increased from undetectable levels to 7.6 and 5.2 nmol/liter, respectively, in P1 and P2. Inhibin B and anti-Müllerian hormone increased to normal levels. Mean testicular volume increased from 0.45 to 0.57 ml at birth to 2.10 ml at 7 months. Stretched penile length increased from 8 to 30 mm (P1) and 12 to 48 mm (P2). CONCLUSIONS: The present regimen induced physiological postnatal testes growth and high-normal activation of Leydig and Sertoli cells.     

Prevalence of testicular adrenal rest tumours in male children with congenital adrenal hyperplasia due to 21-hydroxylase deficiency

OBJECTIVE: Testicular adrenal rest tumours (TART) are a well-known complication in adult male patients with congenital adrenal hyperplasia (CAH), with a reported prevalence of up to 94%. In adulthood, the tumours are associated with gonadal dysfunction most probably due to longstanding obstruction of the seminiferous tubules. The aim of our study was to determine the presence of TART and their influence on gonadal function in childhood. DESIGN: Retrospective study. PATIENTS AND METHODS: Scrotal ultrasound was performed in 34 children with CAH due to 21-hydroxylase deficiency who were between 2 and 18 years old. FSH, LH, testosterone and inhibin B concentrations were measured in serum of 27 patients. RESULTS: TART were detected by ultrasound in 8 out of 34 (24%) children. In two of them, bilateral tumours were found. All lesions were located in the rete testis. Seven patients had the salt-wasting type of CAH; one patient had the simple virilising type of CAH. Mean tumour size was 4.1 mm (range 2-8 mm). In none of the patients were the tumours palpable. Two children with TART were between 5 and 10 years old, the other six children were above 10 years old. In all children with TART, LH, FSH, testosterone and inhibin B levels were similar to the patients without TART. CONCLUSION: TART can be found in CAH children before the age of 10 years. The absence of gonadal dysfunction in our group of children suggests that gonadal dysfunction as frequently reported in adult CAH patients with TART develops after childhood.     

Testicular adrenal rest tumors in adult males with congenital adrenal hyperplasia: evaluation of pituitary-gonadal function before and after successful testis-sparing surgery in eight patients

CONTEXT: In male patients with congenital adrenal hyperplasia (CAH), testicular adrenal rest tumors (TART) are frequently present. These tumors can interfere with testicular function. Intensifying glucocorticoid therapy does not always lead to tumor regression and improvement of testicular function. Recently, testis-sparing surgery was introduced for treatment of TART. OBJECTIVE: The aim of this study was to evaluate tumor volume, symptoms, and pituitary-gonadal function in male patients with CAH caused by 21-hydroxylase deficiency and bilateral TART before and after testis-sparing surgery. SETTING: This study was conducted at Radboud University Nijmegen Medical Centre in The Netherlands. PATIENTS: Eight adult male CAH patients with bilateral TART and infertility were included. INTERVENTIONS: Evaluation of testicular magnetic resonance imaging, symptoms, fasting serum concentrations of ACTH, LH, FSH, inhibin B, 17-OH progesterone, androstenedione, testosterone, and estrone, and semen analysis (six of eight patients) was performed before and 6 and 22 months after testis-sparing surgery. MAIN OUTCOME MEASURES: The main outcome measures were absence of residual tumor and improvement of symptoms and pituitary-gonadal function. RESULTS: Residual tumors were not found on any of the patients' magnetic resonance imaging after surgery. Two patients reported testicular pain and discomfort that disappeared after surgery. Parameters of pituitary-gonadal function did not improve after surgery: semen analysis showed azoospermia (five patients) or oligospermia (one patient) without improvement, and all patients had persistently low inhibin B concentrations. CONCLUSION: Testis-sparing surgery did not improve pituitary-gonadal function despite successful removal of the tumors. Further studies are needed to investigate whether surgery at an earlier stage in the natural history of TART can prevent permanent testicular damage.     

Age-specific changes in sex steroid biosynthesis and sex development

Normal male sex development requires the SRY gene on the Y chromosome, the regression of Müllerian structures via anti-Müllerian hormone (AMH) signalling, the development of the Wolffian duct system into normal male internal genital structures consequent to testosterone secretion by the testicular Leydig cells, and finally, sufficient activation of testosterone to dihydrotestosterone by 5alpha-reductase. All these events take place during weeks 8-12 of gestation, a narrow window of sexual differentiation. Recent studies in human fetal development have demonstrated the early fetal expression of the adrenocorticotrophic hormone (ACTH) receptor and all steroidogenic components necessary for the biosynthesis of cortisol. These findings provide compelling evidence for the assumed pathogenesis of congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency, diminished feedback to the pituitary due to glucocorticoid deficiency, subsequent ACTH excess, and up-regulation of adrenal androgen production with subsequent virilization. Another CAH variant, P450 oxidoreductase deficiency, manifests with 46,XX disorder of sex development (DSD), i.e., virilized female genitalia, despite concurrently low circulating androgens. This CAH variant illustrates the existence of an alternative pathway toward the biosynthesis of active androgens in humans which is active in human fetal life only. Thus CAH teaches important lessons from nature, providing privileged insights into the window of human sexual differentiation, and particularly highlighting the importance of steroidogenesis in the process of human sexual differentiation.     

Low risk of impaired testicular Sertoli and Leydig cell functions in boys with isolated hypospadias

CONTEXT: Isolated hypospadias may result from impaired testicular function or androgen end-organ defects or, alternatively, from hormone-independent abnormalities of morphogenetic events responsible for urethral seam. OBJECTIVE: The objective was to evaluate the relative prevalence of hormone-dependent etiologies in boys with isolated hypospadias. DESIGN, PATIENTS, AND MAIN OUTCOME MEASURES: We studied endocrine testicular capacity in 61 patients with isolated hypospadias and 28 with hypospadias associated with micropenis, cryptorchidism, or ambiguous genitalia. Serum anti-Müllerian hormone and inhibin B were used as Sertoli cell markers. A human chorionic gonadotropin test was performed to evaluate Leydig cell function. RESULTS: Testicular dysfunction was observed in 57.1% and androgen end-organ defects in 7.2% of patients with hypospadias associated with cryptorchidism, micropenis, or ambiguous genitalia. In the remaining 35.7%, the disorder was idiopathic. The presence of ambiguous genitalia predicted the existence of testicular or end-organ dysfunction with 81.8% specificity. Isolated hypospadias was associated in 14.8% of patients with testicular dysfunction and in 6.5% of cases with end-organ defects; in 78.7% of cases, the condition was idiopathic. The occurrence of isolated hypospadias ruled out the existence of testicular or end-organ disorders with 80.0% sensitivity. Altogether our data indicate that the risk for the existence of an underlying testicular or end-organ dysfunction is low in patients with isolated hypospadias (odds ratio, 0.13; 95% confidence interval, 0.05-0.36; P < 0.001). CONCLUSIONS: Boys with isolated hypospadias are more likely to have normal endocrine testicular and androgen end-organ functions, suggesting that transient disruption of morphogenetic events in early fetal life may be the predominant underlying cause.     

Müllerian-inhibiting substance type II receptor expression and function in purified rat Leydig cells.

Müllerian-inhibiting substance (MIS), a gonadal hormone in the transforming growth factor-beta superfamily, induces Müllerian duct involution during male sexual differentiation. Mice with null mutations of the MIS ligand or receptor develop Leydig cell hyperplasia and neoplasia in addition to retained Müllerian ducts, whereas MIS-overexpressing transgenic mice have decreased testosterone concentrations and Leydig cell numbers. We hypothesized that MIS directly modulates Leydig cell proliferation and differentiated function in the maturing testis. Therefore, highly purified rat Leydig and Sertoli cells were isolated to examine cell-specific expression, binding, and function of the MIS type II receptor. These studies revealed that this receptor is expressed abundantly in progenitor (21-day) and immature (35-day) Leydig cells as well as in Sertoli cells. Prepubertal progenitor Leydig cells exhibit high affinity (Kd = 15 nM), saturable binding of MIS. No binding, however, is detected with either peripubertal immature Leydig cells or Sertoli cells at either age. Moreover, progenitor, but not immature Leydig cells, respond to MIS by decreasing DNA synthesis. These data demonstrate that functional MIS type II receptors are expressed in progenitor Leydig cells and support the hypothesis that MIS has a direct role in the regulation of postnatal testicular development.     

Impaired cognitive function in women with congenital adrenal hyperplasia

CONTEXT: Congenital adrenal hyperplasia (CAH) is a disorder with a wide spectrum of severity. OBJECTIVE: The objective of this study was to investigate cognitive function in CAH women. DESIGN: This was a case-control study. Setting: This study was conducted at a tertiary center for pediatric endocrinology at the University Hospital of Copenhagen. PARTICIPANTS: Thirty-five Danish CAH women (age 17-51 yr) were included, and participation rate was 84%. Control women were recruited through the Danish Civil Registration System and matched on age and education. MAIN OUTCOME MEASURES: An abbreviated form of the Wechsler Adult Intelligence Scale was used, i.e. full-scale intelligence quotient (IQ; five of 11 subtests), which included three of six verbal IQ subtests and two of five performance IQ subtests. RESULTS: A significantly lower IQ was found in CAH patients compared with controls with respect to mean full-scale IQ (84.5 vs. 99.1; P < 0.001), mean verbal IQ (86.6 vs. 97.3; P < 0.001), and mean performance IQ (85.7 vs. 101.3; P < 0.001). The salt-wasting CAH group had lower IQ scores than the simple-virilizing CAH group, which reached significance for mean total IQ (81.2 vs. 92.8, P = 0.04) and mean verbal IQ (84.7 vs. 95.5, P = 0.05), and additionally, lower scores than the late-onset CAH group, which reached significance for performance IQ (mean 81.5 vs. 96.2, P = 0.02). CONCLUSIONS: Impaired cognitive function was observed in patients with CAH, especially in salt-wasting CAH. These intriguing findings may reflect adverse effects of hyponatremic episodes, suboptimal postnatal hormone replacement therapy or prenatal adrenal androgen excess, and the potential psychosocial consequences of the disorder.     

Anti-Müllerian hormone in disorders of sex determination and differentiation

Masculinisation of internal and external genitalia during foetal development depends on the existence of two discrete testicular hormones: Leydig cell-secreted testosterone drives the differentiation of the Wolffian ducts, the urogenital sinus and the external genitalia, whereas Sertoli cell-produced anti-Müllerian hormone (AMH) provokes the regression of Müllerian ducts. The absence of AMH action in early foetal life results in the formation of the Fallopian tubes, the uterus and the upper third of the vagina. In 46,XY foetuses, lack of AMH may result from testicular dysgenesis affecting both Leydig and Sertoli cell populations: in this case persistence of Müllerian remnants is associated with ambiguous or female external genitalia. Alternatively, defective AMH action may result from mutations of the genes encoding for AMH or its receptor: in this condition known as Persistent Müllerian Duct Syndrome, testosterone production is normal and external genitalia are normally virilised. Finally, AMH may be normally secreted in intersex patients with defects restricted to androgen synthesis or action, resulting in patients with female or ambiguous external genitalia with no Müllerian derivatives.     

Cloning and expression of cDNA for anti-müllerian hormone.

Messenger RNA, prepared from fetal bovine testicular tissue, was used to construct a cDNA library in lambda gt11 phage. The library was screened with an antibody probe directed against bovine anti-Müllerian hormone and three positive clones were isolated. Cross-hybridizing cDNA inserts carried by clones 4 and 5 (1.2 and 0.08 kilobases long, respectively) code for a fragment of authentic anti-Müllerian hormone, as shown by the ability of the anti-epitope antibodies eluted from fusion protein 4 to bind strongly to anti-Müllerian hormone on immunoblots and by the capacity of anti-epitope antibodies 4 and 5 to precipitate radioiodinated bovine anti-Müllerian hormone. A probe prepared from insert 4 hybridizes with an mRNA present only in tissues that are known producers of anti-Müllerian hormone, such as the fetal testis and adult ovarian follicles. The amount of specific mRNA in tissues of males and females is related to the rate of their anti-Müllerian hormone production. The 2.1-kilobase size of this mRNA species is large enough to code for the Mr 62,000 anti-Müllerian hormone polypeptide chain. Insert 4 also hybridizes with an mRNA of similar size in human and rat fetal testicular tissue. The third isolated clone, clone 8, which does not cross-hybridize with the others, carries a cDNA insert coding for a ubiquitous protein, smaller than anti-Müllerian hormone, with which it apparently shares an epitope.     

Inhibin B and anti-Müllerian hormone, but not testosterone levels, are normal in infants with nonmosaic Klinefelter syndrome

Klinefelter syndrome is a major cause of infertility in the male. Nevertheless, pregnancies were recently obtained by intracytoplasmic injection of sperm retrieved by surgery or ejaculation, underscoring the need to understand the role of Sertoli and Leydig cell secretions during development. In 18 infants with prenatally diagnosed homogenous 47,XXY karyotype, blood samples were taken from birth to 3 yr of age. Inhibin B (INHB), anti-Müllerian hormone (AMH), testosterone, FSH, and LH levels were compared with those in six adolescents with XXY karyotype and reference values established in 215 control infants. In XXY infants FSH, LH, INHB, and AMH did not differ from controls. Testosterone levels during the first trimester exhibited a physiological increase but were lower than in controls (P = 0.0001). Significant correlations were found between testosterone and LH (P < 0001), between INHB and FSH (P = 0.0011), and between AMH and INHB (P = 0.025). In XXY adolescents, AMH and INHB were undetectable. Our findings demonstrate that testosterone secretion is impaired in infants with Klinefelter syndrome. By contrast, INHB and AMH secretions were not altered, which raises the question of the mechanism(s) governing the decline of Sertoli cell function after puberty.     

Ontogeny of human fetal testicular apoptosis during first, second, and third trimesters of pregnancy

During spermatogenesis in human adults, testicular germ cells proliferate, differentiate, and die by apoptosis. However, little is known about the temporal or spatial nature of this programmed cell death. Such information may be useful for understanding prenatal developmental biology as well as spermatogenesis during adulthood, particularly in the context of germ cell disorders. We undertook this study to determine 1) whether apoptosis occurred in a cell-specific fashion in the germ cell population and the supporting somatic cells; and 2) whether apoptosis varied with gestational age. We examined human fetal testicular tissues obtained from 17 karyotypically and structurally normal fetuses of mothers who underwent spontaneous or induced abortions. Three gestational ages were defined as follows: group A, 12-13 wk gestation (n = 5); group B, 20-22 wk gestation (n = 7); and group C, 37-40 wk gestation (n = 5). Morphology in conjunction with in situ end labeling was used to identify and quantify apoptotic nuclei in fetal gonadal tissues. The results of this study suggest that gonadal apoptosis occurred in germ cells, Sertoli cells, and Leydig cells at all gestational ages. Apoptotic death was highest in the Leydig cells, followed by germ cells and Sertoli cells. There was a significant positive correlation between the apoptosis of germ cells and Sertoli cells (P < 0.01) and a negative correlation between healthy germ cells and Sertoli cells (P < 0.001). There was also a negative correlation between the intratubular cell number and the gestational age. Specifically, the proportion of Sertoli cells decreased with gestational age, although there was no significant change in the germ cell in relation to gestational age. No such relationship was found in the Leydig cell population, all of which reside outside the seminiferous tubules. These results are the first to suggest that fetal testicular apoptosis begins in the first trimester, occurs in the three major cell types, and continues throughout pregnancy. Our data also suggest that in the fetal gonad, germ and Sertoli cell proliferation and death may be controlled by a genetic program distinct from that of the Leydig cells. This information is relevant to the understanding of abnormal spermatogenesis associated with infertility and to germ cell tumors in adult life.     

Klinefelter syndrome in adolescence: onset of puberty is associated with accelerated germ cell depletion

The process of germ cell depletion in patients with Klinefelter syndrome (KS) is incompletely characterized. In the current work, we evaluated the presence of germ cells in adolescent boys with KS for possible future use in assisted reproduction techniques. Fourteen nonmosaic 47,XXY boys (aged 10-14 yr) were enrolled. Every fourth month their puberty was staged, and serum was obtained for hormone analyses. Each boy underwent a single testicular biopsy. Biopsy specimens of seven peripubertal boys (testicular volume < 2.0 ml) had spermatogonia of adult type, whereas older boys with larger testes (> 2.0 ml) exhibited no germ cells. No meiotic germ cells were detectable in any of these subjects. Depletion of germ cells was associated with an increase in testicular volume but was not immediately reflected in levels of serum gonadotropin, inhibin B, or anti-Müllerian hormone. In contrast, hypergonadotropism and suppression of serum inhibin B and anti-Müllerian hormone developed later, during midpuberty, after an unequivocal increase in serum testosterone (>2.5 nmol/liter) levels and degeneration of Sertoli cells. In conclusion, these prepubertal and early pubertal boys with KS had diploid germ cells that vanished in early puberty when testicular volume increased, whereas serum gonadotropin and inhibin B levels displayed pathological changes later during midpuberty.     

Growth hormone therapy alone or in combination with gonadotropin-releasing hormone analog therapy to improve the height deficit in children with congenital adrenal hyperplasia

Short stature in the adult patient with congenital adrenal hyperplasia (CAH) is commonly seen, even among patients in excellent adrenal control during childhood and puberty. In this study we examine the effect of GH therapy on height prediction in children with both CAH and compromised height prediction. Leuprolide acetate, a GnRH analog (GnRHa), was given to patients with evidence of early puberty. GH (n = 12) or the combination of GH and GnRHa (n = 8) was administered to 20 patients with CAH while they continued therapy with glucocorticoids. Each patient in the treatment group was matched according to age, sex, bone age, puberty, and type of CAH with another CAH patient treated only with glucocorticoid replacement. The match was made at the start of GH treatment. Of the 20 patients, 12 have completed 2 yr of therapy. After 1 yr of GH or combination GH and GnRHa therapy, the mean growth rate increased from 5 +/- 1.9 to 7.8 +/- 1.6 cm/yr vs. 5.4 +/- 1.7 to 5 +/- 2 cm/yr in the group not receiving GH (P < 0.0001). During the second year of treatment, the mean growth rate was 6 +/- 1.6 vs. 4.2 +/- 2.1 cm/yr in the group not receiving GH (P < 0.001). The height SD score for chronological age in the treatment group at the end of 1 and 2 yr of treatment improved significantly more than the nontreatment group (P < 0.01). A similar improvement in the height SD score for bone age was found in the treatment group after 1 (-1.4 +/- 0.9 vs. -1.7 +/- 0.9; P < 0.0001) and 2 yr of therapy (-0.67 +/- 0.68 vs. -1.7 +/- 1.2; P < 0.0004). The mean predicted adult height improved from 159 +/- 11 (baseline) to 170 +/- 7.5 cm (after 2 yr of therapy) closely approximating target height (173 +/- 8 cm). All patients continued the hydrocortisone treatment. In patients with CAH and compromised height prediction, treatment with GH or the combination of GH and GnRHa results in an improvement of growth rate and height prediction and a reduction in height deficit for bone age.     

Evaluation of gonadal function in 107 intersex patients by means of serum antimüllerian hormone measurement

Fetal male sexual differentiation is driven by two testicular hormones: testosterone (synthesized by interstitial Leydig cells) and antimüllerian hormone (AMH; produced by Sertoli cells present in the seminiferous tubules). Intersex states result either from gonadal dysgenesis, in which both Leydig and Sertoli cell populations are affected, or from impaired secretion or action of either testosterone or AMH. Until now, only Leydig cell function has been assessed in children with ambiguous genitalia, by means of testosterone assay. To determine whether serum AMH would help in the diagnosis of intersex conditions, we assayed serum AMH levels in 107 patients with ambiguous genitalia of various etiologies. In XY patients, AMH was low when the intersex condition was caused by abnormal testicular determination (including pure and partial gonadal dysgenesis) but was normal or elevated in patients with impaired testosterone secretion, whereas serum testosterone was low in both groups. AMH was also elevated during the first year of life and at puberty in intersex states caused by androgen insensitivity. In 46,XX patients with a normal male phenotype or ambiguous genitalia, in whom the diagnosis of female pseudohermaphroditism had been excluded, serum AMH levels higher than 75 pmol/L were indicative of the presence of testicular tissue and correlated with the mass of functional testicular parenchyma. In conclusion, serum AMH determination is a powerful tool to assess Sertoli cell function in children with intersex states, and it helps to distinguish between defects of male sexual differentiation caused by abnormal testicular determination and those resulting from isolated impairment of testosterone secretion or action.     

The prevalence of testicular adrenal rest tumors and associated factors in postpubertal patients with congenital adrenal hyperplasia caused by 21-hydroxylase deficiency

Development of a testicular adrenal rest tumor (TART) is common in males with congenital adrenal hyperplasia, and it can be an important cause of infertility. In the present study, we observed the prevalence of TARTs, and analyzed its associated factors in patients with 21-hydroxylase deficiency. Testicular ultrasonography was performed in 48 postpubertal male patients aged 10.6 to 27.1 years. To determine whether patients were undertreated, we analyzed the serum 17-hydroxyprogesterone (17-OHP) levels to the time of ultrasonographic measurement and calculated the percentage of measurements when serum 17-OHP level was >10 ng/mL relative to the total number of measurements during the follow-up period. We divided the 6-year period before ultrasonographic measurement (time 0) into three 2-year intervals and calculated the average concentration of serum 17-OHP in each interval to give a -2(nd) to 0 year-average concentration (-2-0YAC), -4-2YAC and -6-4YAC. A TART was detected by ultrasonography in 31 of 48 patients (64.6%) and the median maximal cross-sectional area of the TARTs was 0.71 (0.03, 4.95) cm(2). The corrected final adult height was lower, and -4-2YAC and body mass index were higher in patients with TART than in those without. After controlling for the type of 21-hydroxylase deficiency, hydrocortisone-equivalent dose, age, and -6-4YAC, the size of TART was associated with a high undertreatment percentage with a marginal statistical significance. These results suggest that strict disease control is mandatory and regular examination with testicular ultrasonography is recommended in male patients, regardless of the type of 21-hydroxylase deficiency.     

PERSISTENCE OF MÜLLERIAN DUCTS IN MALE PSEUDOHERMAPHRODITISM, AND ITS RELATIONSHIP TO CRYPTORCHIDISM

Twenty-two cases of male pseudohermaphroditism with persistence of Müllerian duct derivatives were reviewed. In 12 cases of mixed gonadal dysgenesis and five cases of dysgenetic male pseudohermaphroditism, testosterone-dependent steps of sex differentiation were also impaired, and testicular dysgenesis was prominent, even in the younger age group. The capacity of testes to inhibit the ipsilateral Müllerian duct was correlated with testicular descent: it is suggested that testicular dysgenesis explains both the functional and topographical testicular abnormalities observed in these male pseudohermaphrodites. Five other patients were cryptorchid but externally normally virilised, persistence of Müllerian derivatives representing their only abnormality of sex differentiation. Testicular structure was usually normal or showed changes attributable to long-standing cryptorchidism. It is suggested that in these patients, persistence of Müllerian derivatives is due to an inborn error of metabolism, affecting the binding of anti-Müllerian hormone to its receptor and that failure of testicular descent is caused by mechanical restraint by the abdominal Müllerian organs.     

Experimental control of the differentiation of Leydig cells in the rat fetal testis.

In the developing fetal testis, in vitro as well as in vivo, two kinds of endocrine cells differentiate successively: Sertoli cells, which produce the Müllerian inhibitor (or anti-Müllerian hormone) and aggregate with germ cells into seminiferous cords; and Leydig cells, which release androgens. Serum added to the synthetic culture medium prevents the morphogenesis of the seminiferous cords but not the cytodifferentiation of the endocrine cells. L-Azetidine 2-carboxylic acid (LACA), a proline competitor, introduced into the medium also prevents differentiation of seminiferous cords. In the present experiments, the effects of LACA on the endocrine cells were studied. It did not suppress production of the Müllerian inhibitor, but it opposed differentiation of Leydig cells. Histochemically detectable 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) was virtually absent and the release of testosterone, delta 4-androstenedione, 17-hydroxyprogesterone, or progesterone into the medium became undetectable. Moreover, dibutyryl cAMP added to the medium during the final day in vitro had very little effect on the parameters of steroidogenesis. An excess of proline added to the LACA-containing medium permitted normal morphogenesis of seminiferous cords, normal steroidogenesis, and normal response to cAMP. LACA did not prevent the appearance of 3 beta-HSD activity in the adrenals, nor did it reduce the expression of laminin and fibronectin (data not shown) in the mesonephric structures as much as in the testes. The differentiation of the testis and especially of the Leydig cells appears to have special requirements for proline.     

Ageing, testicular tumours and the pituitary-testis axis in dogs

Dogs of different ages without testicular diseases were evaluated to study possible age-related changes in hormone concentrations in serum. Dogs with testicular tumours were also investigated to study the relation between tumour type and hormone concentrations; in this study, dogs with Sertoli cell tumours, Leydig cell tumours and seminomas were included. We measured testosterone, oestradiol, LH, FSH and inhibin-like immunoreactivity concentrations in peripheral venous and testicular venous blood of these animals. In normal dogs there appeared to be no age-related changes in the concentrations of the investigated hormones, except for a significant age-related decrease in oestradiol concentrations in testicular venous blood (P<0.02). Dogs with a Sertoli cell tumour had greater oestradiol concentrations and inhibin-like immunoreactivity in both peripheral and testicular venous blood than did dogs without a neoplasm (P<0. 05). Testosterone concentrations were reduced in dogs with Sertoli cell tumours, as were FSH and LH. Feminisation occurred in eight of 13 dogs with a Sertoli cell tumour and in two of 14 dogs with a Leydig cell tumour; it was accompanied by a significantly greater oestradiol concentration than in normal dogs and in dogs with Sertoli cell tumours without signs of feminisation. Dogs with a Leydig cell tumour had greater concentrations of oestradiol and inhibin-like immunoreactivity in both peripheral venous and testicular venous blood than did dogs without a neoplasm (P<0.05). The testosterone concentration in testicular venous blood of these dogs was lower than that in dogs with normal testes. The concentration of LH in peripheral venous blood was also reduced (P<0. 05). Hormone concentrations in dogs with a seminoma were not different from those in normal dogs. It was concluded that seminomas are not endocrinologically active. In contrast, both Sertoli cell tumours and Leydig cell tumours can cause increased oestrogen production leading to signs of feminisation. These tumours also have considerable amounts of inhibin-like immunoreactivity, but only in Sertoli cell tumours does this result in a reduction in FSH concentrations, suggesting that Sertoli cell tumours secrete dimeric inhibin, whereas Leydig cell tumours presumably produce loose alpha-subunits that cross-react in the inhibin assay but are not biologically active.