The lh-hcg receptor of human ovary at various stages of the menstrual cycle.

Receptors specific for hCG were found in human corpora lutea and follicles. hCG and LH were found to bind at a similar receptor site. The dissociation constant for hCG ranged from 10-minus 10 to 10-minus 11 mol/1 in human corpora lutea. The number of binding sites for 125-I-hCG ranged from 10-minus 14 to 10-minus 15 moles/mg protein in human corpora lutea. The binding of 125-I-hCG to ovary was found to vary at different stages of the menstrual cycle. The binding of 125-I-hCG to human ovaries increased on days 13-15 of the cycle, then declined slightly, and increased again on days 22-23. Following day 23, there was a slow decline until day 27 when binding activity could no longer be measured. No binding could be measured by the corpus luteum after the onset of menstruation or in corpora albicans.     

Variable ovarian response to gonadotropin-releasing hormone antagonist-induced gonadotropin deprivation during different phases of the menstrual cycle

The gonadotropin dependence of ovarian follicular maturation and corpus luteum function can now be examined in women using antagonistic analogs of GnRH. We studied the responses of three groups of women throughout a control cycle and during the administration of a potent GnRH antagonist, detirelix ([N-Ac-D-Nal(2)1,D-pCl-Phe2,D-Trp3,D-hArg(Et2)6,D-Ala10++ +] GnRH, Syntex Research). Detirelix (10 mg, sc) was administered for 3 consecutive days during the midfollicular phase (n = 4), preovulatory phase (n = 4), and early luteal phase (n = 4). The pituitary response to detirelix was similar throughout the three phases of the menstrual cycle. Immunoreactive LH concentrations decreased to 35% (mean +/- SEM) of pretreatment values within 8 h after the initial injection and remained suppressed for 72 h after discontinuance of treatment. Immunoreactive FSH concentrations decreased to 73 +/- 3% of pretreatment levels within 8 h and returned to baseline within 24 h after the third injection. In contrast, the ovarian response to detirelix varied markedly during different phases of the cycle. Midfollicular phase treatment was associated with a decline in estradiol (E2) levels from pretreatment values of 246 +/- 48 to 81 +/- 15 pmol/L within 24 h of the last injection. Vaginal bleeding ensued in three of four women. Follicular recruitment was then reinitiated, and an ovulatory LH surge occurred 18.2 +/- 2.9 days after the last injection. Similarly, treatment during the early luteal phase produced a decline in E2 concentrations from 286 +/- 29 to 70 +/- 7 pmol/L and a decline in progesterone concentrations from 20 +/- 1.6 to 1.9 +/- 0.3 nmol/L within 24 h after the last injection. Luteolysis was associated with menstrual bleeding in all four women. The subsequent ovulatory LH surge occurred 16.5 +/- 1.0 days after discontinuance of treatment. In contrast, treatment during the preovulatory phase resulted in a decline in E2 concentrations from 844 +/- 66 to 429 +/- 132 pmol/L during the first 48 h of treatment. Gonadotropin and E2 concentrations subsequently recovered from suppression, growth of the dominant follicle resumed, and a LH surge occurred 5.8 +/- 1.4 days after the last injection. These data indicate that the GnRH antagonist detirelix produces rapid and consistent suppression of pituitary gonadotropin secretion. The magnitude of suppression and preferential suppression of LH vs. FSH are similar throughout the cycle. In contrast, the ovarian response to gonadotropin deprivation varies during the menstrual cycle.(ABSTRACT TRUNCATED AT 400 WORDS)     

Simultaneous increases of leptin and gonadotropin-releasing hormone following exogenous estrogen administration in women with normally menstrual cycle

The aim of this study was to investigate whether administration of exogenous estrogen affects the changes of leptin and GnRH levels in women with normal menstrual cycle. A total of 18 women received a bolus intravenous injection of 20 mg conjugated estrogen (premarin group) at 0800 during the fifth day of menstrual cycle, while another 18 women were administered 20 mL of normal saline as the control group. Fasting blood samples were collected at 0, 4, 8, 24, 28, 32, 48, 56, 72 and 96 hours after injection for analyses of leptin, GnRH, estrone (E(1)), estradiol (E(2)), LH and FSH. Both the mean plasma levels of E(1) and E(2) were significantly increased from 4 hours and significantly sustained elevated levels up to 72 hours after injection of premarin. Simultaneous significant increases of leptin and GnRH levels were observed at 28, 32 and 48 hours after injection, while the controls remained constant. The mean LH and FSH levels were initially suppressed and then significantly increased at 56 and 72 hours after premarin administration. Leptin appears to be involved in the regulation of positive feedback mechanism of estrogen by conveyance of metabolic signal to affect the release of GnRH in hypothalamus, while its participation in the modulation of negative feedback remains unknown.     

Immunohistochemical analysis of human uterine estrogen and progesterone receptors throughout the menstrual cycle

Estrogen receptors (ER) and progesterone receptors (PgR) were studied immunohistochemically using specific antireceptor monoclonal antibodies in uterine tissue samples from 33 women in various stages of the menstrual cycle. Immunohistochemical localization was quantified as to intensity of staining and tissue distribution in glandular epithelium, stroma, and myometrium, and the results were compared with those of standard ligand binding assays. In all samples ER and PgR localized within the nuclei of target cells. The maximal concentrations of ER and PgR occurred in the mid- to late proliferative phase of the menstrual cycle. ER content declined throughout the secretory phase. In contrast, PgR content underwent unexpectedly complex and dyssynchronous fluctuations during the secretory phase of the menstrual cycle. Specifically, the glandular epithelium had diminished PgR content, while the stroma and myometrium maintained a significant PgR content. PgR and perhaps ER are not concordant in different cell types within the uterus. Segregation of function through alteration of receptor content may be an important mechanism in steroid-dependent growth and differentiation of target tissues.     

Growth hormone and prolactin response to ghrelin during the normal menstrual cycle

Objective  It has been suggested that exogenous oestradiol augments ghrelin-induced growth hormone (GH) secretion in postmenopausal women. Whether endogenous oestrogens exert a similar effect during the normal menstrual cycle is not known. The aim of this study was to test the hypothesis that physiological changes in ovarian steroids during the normal menstrual cycle modulate GH and prolactin (PRL) response to ghrelin.
Design  Healthy women were studied in three phases of the normal menstrual cycle.
Patients  Ten healthy normally cycling women.
Measurements  A single dose of ghrelin (1 µg/kg) was administered intravenously in the early and late follicular phases and in the mid-luteal phase of the cycle. Saline was injected in the preceding cycle. Blood samples were taken before ghrelin or saline injection (time 0) and also at –15, 15, 30, 45, 60, 75, 90 and 120 min. The GH and PRL responses were assessed.
Results  Serum oestradiol and progesterone concentrations showed the variations of a normal menstrual cycle. After ghrelin administration, in the three phases of the cycle, plasma ghrelin and serum GH and PRL levels increased rapidly, peaking at 30 min and declining gradually thereafter ( P <  0·001). There were no significant differences in the hormone levels between the three phases at all time points. No changes in GH and PRL levels were seen after saline injection.
Conclusions  These results demonstrate that GH and PRL responses to ghrelin do not change across the menstrual cycle. It is suggested that the action of ghrelin on the pituitary somatotrophs is modulated differentially by endogenous and exogenous ovarian steroids.     

Cyclical secretion of prorenin during the menstrual cycle: synchronization with luteinizing hormone and progesterone.

Plasma prorenin, a high molecular weight precursor form of renin, (renin, EC 3.4.23.15; old number, EC 3.4.99.19), was measured three times weekly in normal young women during the menstrual cycle and was related to changes in luteinizing hormone, estradiol, and progesterone. In all subjects a stable baseline level of prorenin occurred during the follicular phase. Then, simultaneously or soon after the luteinizing hormone peak, plasma prorenin consistently increased about 2-fold. Baseline prorenin ranged from 18 to 40 ng per ml per hr, and peak prorenin ranged from 35 to 65 ng per ml per hr. The maximum increase in prorenin averaged 80%. Prorenin remained elevated during the mid-luteal phase of the menstrual cycle and returned to baseline during the late-luteal phase in coordination with the decrease in progesterone. The changes in prorenin were not synchronized with changes in active renin which was significantly increased only during the mid-luteal phase. These findings suggest that prorenin may be involved in reproductive physiology.     

Cortisol, 17 alpha-OH, progesterone and androgen responses to a standardized ACTH-stimulation in different stages of the normal menstrual cycle

The release of cortisol, 17 alpha-OH-progesterone, androstenedione and testosterone during a standardized ACTH-stimulation test was investigated in three different stage of the normal menstrual cycle, to conclude if there is any stage dependency on the release of these hormones. No statistically significant differences were observed between the three stages concerning cortisol and testosterone increase. The increase of androstenedione in the pre-ovulatory stage was significantly high than that seen during the early follicular phase of the cycle. The increase of 17 alpha-OH-progesterone in the luteal phase was significantly less than that of both the early and late follicular stages of the cycle. Progesterone levels showed a small, but significant increase after ACTH-stimulation, in both the early and late stage of the follicular phase. However, the levels remained within the normal range of the follicular phase. In the luteal phase no increase was seen after ACTH-stimulation. Oestradiol-17 beta levels did not change at all after ACTH stimulation. The stage dependency of androstenedione and 17 alpha-OH-progesterone is discussed. The described stage-dependency different increase of 17 alpha-OH-progesterone release can be of importance when the results of ACTH-tests are evaluated to detect carriers of congenital adrenal hyperplasia.     

Sex steroid priming effects on growth hormone response to pyridostigmine throughout the menstrual cycle.

To explore the effect of estradiol and progesterone on the GH response to the indirect cholinergic agonist pyridostigmine nine healthy women were challenged with both active drug and placebo at three time points in two consecutive menstrual cycles: a total of six neuroendocrine tests. A randomized, double-blind, counterbalanced design was used. Subjects were tested in the early follicular, mid-cycle, and luteal phases of the cycle. A cannula was inserted in a forearm vein after an overnight fast and baseline GH, estradiol, and progesterone samples were drawn. After 120 mg oral pyridostigmine or placebo tablets further blood samples for GH analysis were drawn at intervals over 3 h. When expressed as maximum change from baseline (delta GH) mean GH responses to pyridostigmine increased incrementally from early (8.4 +/- 2.7 micrograms/L) through mid (18 +/- 1.3 micrograms/L) to late (22.2 +/- 1.9 micrograms/L) cycle. This represents a significant effect of cycle phase on the GH response to pyridostigmine (P less than 0.001, as assessed by analysis of variance). Responses to placebo did not vary. Plasma estradiol values were significantly correlated with GH responsivity to active drug throughout the cycle (P less than 0.02). Multiple regression analysis also revealed a significant positive correlation between progesterone levels and GH response to pyridostigmine (P less than 0.02). Estrogens augment GH responses to other challenges but a priming effect of progesterone on GH responsivity has not previously been demonstrated. Various mechanisms are discussed including a possible sex steroid priming effect on acetylcholine neurotransmission.     

Prolactin-releasing action of a low dose of exogenous gonadotropin-releasing hormone throughout the human menstrual cycle

Pharmacological doses of gonadotropin-releasing hormone (GnRH) are known to induce prolactin (PRL) release in different pathological states. The same effect can be observed in postmenopausal women and during the phases of menstrual cycle characterized by high estrogen levels. With the aim to evaluate whether nonpharmacological doses of GnRH are also able to induce PRL release, gonadotropin and PRL response to a low dose of GnRH (10 micrograms, i.v. bolus) was evaluated in 70 normal women during different phases of their menstrual cycle. A significant PRL increase was observed in 33% of subjects during the first days of the cycle (menstrual phase; days 1-3 from the beginning of menstrual bleeding: n = 6), in 24% of subjects during early follicular phase (days -10 to -8 from LH peak: n = 17); in 38% of subjects during midfollicular phase (days -6 to -4 from LH peak: n = 8); in 78% of subjects during preovulatory phase (days -2 to -1 from LH peak; n = 9); in 67% of subjects during postovulatory phase (days +1 to +2 from LH peak; n = 6) and in 42% of subjects during midluteal phase (days +5 to +8 from LH peak; n = 24). In brief, the increase of mean PRL levels after GnRH administration was only significant (p less than 0.05) during pre- and postovulatory phases. The percentage of patients who showed a PRL response during the different phases of menstrual cycle was significantly correlated to the mean maximal net increase of LH (r = 0.927; p less than 0.01) and to the mean maximal net increase of FSH (r = 0.926; p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Expression of estrogen receptor alpha and beta in the rhesus monkey corpus luteum during the menstrual cycle: regulation by luteinizing hormone and progesterone

There are conflicting reports on the presence or absence of estrogen receptor (ER) in the primate corpus luteum, and the discovery of a second type of estrogen receptor, ERbeta, adds an additional level of complexity. To reevaluate ER expression in the primate luteal tissue, we used semiquantitative RT-PCR based assays and Western blotting to assess ERalpha and beta messenger RNA (mRNA) and protein levels in corpora lutea (n = 3/stage) obtained from adult female rhesus monkeys at early (days 3-5), mid (days 6-8), mid-late (days 10-12), and late (days 14-16) luteal phase of the natural menstrual cycle. ERalpha mRNA levels did not vary across the stages of the luteal phase, and ERalpha protein was not consistently detected in luteal tissues. However, ERbeta mRNA and protein levels were detectable in early and mid luteal phases and increased (P < 0.05) to peak levels at mid-late luteal phase before declining by late luteal phase. To determine if ERbeta mRNA expression in the corpus luteum is regulated by LH, monkeys received the GnRH antagonist antide either alone or with 3 daily injections of LH to simulate pulsatile LH release. Treatment with antide alone or concomitant LH administration did not alter luteal ERbeta mRNA levels. When monkeys also received the 3beta-hydroxysteroid dehydrogenase inhibitor trilostane to reduce luteal progesterone production, luteal ERbeta mRNA levels were 3-fold higher (P < 0.05) than in monkeys receiving antide + LH only. Replacement of progestin activity with R5020 reduced luteal ERbeta mRNA levels to those seen in animals receiving antide + LH. Thus, there is dynamic ERbeta expression in the primate corpus luteum during the menstrual cycle, consistent with a role for estrogen in the regulation of primate luteal function and life span via a receptor (ERbeta)-mediated pathway. Increased ERbeta expression in the progestin-depleted corpus luteum during LH exposure suggests that the relative progestin deprivation experienced by the corpus luteum between LH pulses may enhance luteal sensitivity to estrogens during the late luteal phase of the menstrual cycle.     

The relationship of changes in serum estradiol and progesterone during the menstrual cycle to the thyrotropin and prolactin responses to thyrotropin-releasing hormone.

The responses of serum TSH and PRL to TRH (500 microgram) were studied in normal young women in the early follicular, periovulatory, and midluteal phases of the menstrual cycle in order to examine the relationship of these responses to the levels of estradiol relationship of these responses to the levels of estradiol (E2) and progesterone. Each woman was studied twice in each phase in order to assess intraindividual variability. There was no significant difference in either the TSH or PRL responses among the phases of the menstrual cycle nor was either response affected by the periovulatory rise in E2 or by the luteal rise in both E2 and progesterone. Thus, the interpretation of the TSH and PRL responses to TRH in normal women is not affected by the menstrual cycle although both responses are greater in women that in men. Both the peak TSH and peak PRL after TRH were highly correlated with the basal levels of TSH (r = 0.85; P less than 0.01) and PRL (r = 0.67; P less than 0.01), respectively, indicating that the TSH and PRL responses to TRH in women are directly proportionate to the basal levels of the respective hormones, as previously shown for the TSH response in men. The mean intraindividual variability (coefficient of variation) of the TSH response to TRH was 18%, but ranged as high as 56%, while that of the PRL response was 16% and ranged up to 31%; variability was not affected by the phase of the menstrual cycle. The normal range of the peak TSH after TRH in women is 7-33 microU/ml (mean +/- 2 SD); however, because of the variability, a normal woman may sometimes have a peak TSH after TRH as low as 4 microU/ml. Repeating the test will result in a normal value if the woman is truly normal. Similarly, the normal peak PRL after TRH in women is 22-111 ng/ml (mean +/- 2 SD); usually, however, the lower limit is 30 ng/ml with lower values due to intraindividual variation. The data suggest that the higher average level of E2 in women compared to women, but that the cyclic changes in serum E2 or progesterone in women have little or no additional effect.     

Radiotelemetric monitoring of hypothalamic gonadotropin-releasing hormone pulse generator activity throughout the menstrual cycle of the rhesus monkey

Continuous monitoring of the electrophysiological manifestations of GnRH pulse generator activity was achieved by radiotelemetry throughout the menstrual cycles of unrestrained rhesus monkeys. The characteristic increases in hypothalamic multiunit activity (MUA volleys) associated with each LH pulse measured in the peripheral circulation were of lower frequency during the luteal phase than in the follicular phase of the cycle. Multiunit activity volley frequency increased as functional luteolysis progressed and achieved maxima of approximately one volley per hour within the first few days of the follicular phase. Unexpectedly, a dramatic decline in pulse generator frequency was observed coincidentally with the initiation of the preovulatory LH surge. Evidence is presented to support the conclusion that this deceleration of pulse generator activity is the consequence of the preovulatory rise in plasma estrogen concentration. As reported in women, a significant reduction in GnRH pulse generator frequency was observed at night during the follicular phase, but not during the luteal phase, of the menstrual cycle.     

Predicting the response of growth hormone-deficient children to long term treatment with human growth hormone.

A previous study showed that when GH-deficient children below the third percentile in height are treated with 0.168 U human GH (hGH)/kg BW3/4 for 10 days, their height increases by 0.3--1.9 cm during the next 8 weeks. The present study determined whether this acute response would predict the child's long term response to 1 yr of treatment with the same dose of hGH given three times a week. Eighteen GH-deficient children and adolescents, aged 8--16 yr, were measured every 2 weeks over 108 weeks. After a control period of 12 weeks (period 1), the patient received hGH for 10 days. During the remainder of the 12 weeks of period 2 and during the next 12 weeks (period 3), hGH was not given. Patients recieved hGH three times a week during periods 4 and 5 (24 weeks each). Periods 6 and 7 (12 weeks each) were posttreatment control periods. During periods 1, 3, 6, and 7, rate of growth was less than 0.2 cm/month. During period 2, the rate ranged between 0.1--0.8 cm/month. During periods 4 and 5, the growth rate ranged from 0.2--1.0 cm/month. Rate of growth during periods 4 and 5 (y) was related to rate during period 2 (x) by the equation y = 0.027 + 1.17 x. The correlation coefficient between y and x was 0.91 (P less than 0.001). The increment in height which will occur during 48 weeks of treatment can be predicted from the response to 10 days of treatment by this equation. The SE of the prediction averages +/- 1.2 cm/yr.     

Hemostatic status and fibrinolytic response potential at different phases of the menstrual cycle.

Coagulation and fibrinolytic variables including platelet function and endogenous fibrinolytic response were determined in 30 normal healthy women volunteers not on any known medication during the period of study. They were between 18 years and 38 years old and had normal menstrual cycles of between 28 days and 30 days. Blood samples were obtained within one menstrual cycle and after having fasted overnight within days 1 to 3 (menstruation), 5 to 9 (follicular), 10 to 14 (mid-cycle), and 21 to 26 (luteal) of the menstrual cycle. Analysis of variance (ANOVA) showed no significant differences in the hemostatic parameters studied between the phases of the menstrual cycle except for a reduced D-dimer level at midcycle. Significant fibrinolytic response was seen after venous occlusion but they were not significantly different between the phases of the menstrual cycle. The women were then divided into either normal weight (n=22) or overweight (n=8) according to World Health Organization (WHO) classification and the data reanalyzed. Elevated tissue plasminogen activator antigen and plasminogen activator inhibitor-1 levels except at menstruation and total protein S except at follicular phase were observed in overweight women together with increased plasminogen level only at luteal phase. Significant endogenous fibrinolytic response seen during the menstrual cycle was not different between normal and overweight women. The study demonstrated that systemic coagulation, fibrinolysis, and platelet function were probably not influenced by natural hormonal changes occurring during the menstrual cycle except for an associated reduced fibrinolytic state at mid-cycle. The hemostatic system in this small group of healthy overweight women studied appeared to be physiologically compromised.