Serum LH Responses Research Articles

DON’T BE TRIGGER SHY: A LOW SERUM LUTEINIZING HORMONE (LH) RESPONSE TO GONADOTROPIN-RELEASING HORMONE AGONIST (GnRH-A) HITS THE MARK IN PRE-IMPLANTATION GENETIC TESTING FOR ANEUPLOIDY (PGT-A)

The use of GnRH-a trigger in antagonist controlled ovarian hyperstimulation (COH) cycles has increased due to its enhanced safety profile. However, response, as measured by the serum LH level post trigger, vary considerably1-6. We investigated the impact of serum LH response to GnRH-a trigger in antagonist COH cycles on oocyte yield, oocyte maturity, blastocyst formation, PGT-A and pregnancy outcomes.

Reproductive physiology of a humanized GnRH receptor mouse model: application in evaluation of human-specific analogs

The human GnRH receptor (GNRHR1) has a specific set of properties with physiological and pharmacological influences not appropriately modeled in laboratory animals or cell-based systems. To address this deficiency, we have generated human GNRHR1 knock-in mice and described their reproductive phenotype. Measurement of pituitary GNRHR1 transcripts from homozygous human GNRHR1 knock-in (ki/ki) mice revealed a severe reduction (7- to 8-fold) compared with the mouse Gnrhr1 in wild-type mice. ¹²⁵I-GnRH binding assays on pituitary membrane fractions corroborated reduced human GNRHR1 protein expression in ki/ki mice, as occurs with transfection of human GNRHR1 in cell lines. Female homozygous knock-in mice displayed normal pubertal onset, indicating that a large reduction in GNRHR1 expression is sufficient for this process. However, ki/ki females exhibited periods of prolonged estrous and/or metestrous and reduced fertility. No impairment was found in reproductive maturity or adult fertility in male ki/ki mice. Interestingly, the serum LH response to GnRH challenge was reduced in both knock-in males and females, indicating a reduced GNRHR1 signaling capacity. Small molecules targeting human GPCRs usually have poor activities at homologous rodent receptors, thus limiting their use in preclinical development. Therefore, we tested a human-specific GnRH1 antagonist, NBI-42902, in our mouse model and demonstrated abrogation of a GnRH1-induced serum LH rise in ki/ki mice and an absence of effect in littermates expressing the wild-type murine receptor. This novel model provides the opportunity to study the human receptor in vivo and for screening the activity of human-specific GnRH analogs.

The Effect of Parity of the Dam on Sexual Maturation, Serum Concentrations of Metabolic Hormones and the Response to Luteinizing Hormone Releasing Hormone in Bull Calves

The objectives of this study were to determine the effect of parity of the dam on age at which a scrotal circumference (SC) ≥ 28 cm was attained and the LH response to Luteinizing Hormone Releasing Hormone (LHRH) in bull calves. We also wanted to confirm, in a large group of bull calves, that the LH response to LHRH could be used to select early maturing bulls. Body weight and SC of the bull calves were measured every other week. At 15, 20 and 25 weeks of age, calves received 4.12 nm/kg body weight of LHRH ischio-rectally and blood samples were taken every 15 min for 4 h. Calves from primiparous and multiparous dams were separated into two sub-groups based on age at which an SC ≥ 28 cm was attained (early or late). An SC ≥ 28 cm was attained earlier in calves born to multiparous as compared with primiparous dams (p < 0.05). At 20 and 25 weeks of age, peak serum LH concentrations (LH-peak) and area under the LH response curve (LH-AUC) in response to LHRH were higher (p < 0.01) in calves born to multiparous as compared with primiparous dams. In calves born to multiparous dams the LH-peak at 15 and 25 weeks of age and the LH-AUC at 15 weeks of age were lower (p < 0.05) in calves that attained an SC ≥ 28 cm early as compared with late. The LHRH-challenge test sensitivity and specificity ranged from 46% to 86%. We concluded that parity of the dam affected age at which SC ≥ 28 cm was attained and the LH response to LHRH in bull calves. Serum LH responses to LHRH at 15 and 25 weeks of age, in calves born to multiparous dams, show some promise for development into a test to select early maturing bull calves.

Altered Kinetics of Pituitary Response to Gonadotropin-Releasing Hormone in Women with Variant Luteinizing Hormone: Correlation with Ovulatory Disorders

Objective: The LH response of pituitary gland to gonadotropin-releasing hormone (GnRH) stimulation is not well defined in patients with mutant β-subunit (Trp⁸ to Arg⁸ and Ile¹⁵ to Thr¹⁵). Here we compared the relative activities and dynamics of LH secretion in patients with wild-type and variant LH following injection of GnRH. Methods: A GnRH stimulation test was performed in 33 patients with ovulatory disorders (patient group) and 29 women with normal ovulatory cycles (control group) heterozygous for the variant LHβ allele. Blood samples were obtained up to 120 min after GnRH injection. Serum LH response was determined by comparing the results of LH immunoassays using a monoclonal antibody that recognizes wild-type LH only with those of another assay using a polyclonal antibody that recognizes equally both variant and wild-type LH (total LH). The ratio of variant LH to total LH (LH ratio) was used to determine the serum LH status. Results: The LH ratio in the control group showed the peak 15 min after GnRH injection, while that in the patient group showed the peaks 30–60 min after injection. The LH ratio in the patient group at 120 min after injection was significantly lower than that in the control group. The percent increases in LH ratio in both groups showed the peak 15 min after injection. The patient group had significantly lower changes of LH ratio at 15, 60, 90 and 120 min after GnRH injection compared with that in the control group. Conclusion: Differences in circulatory kinetics of the two types of LH may explain the differences in LH function between patients with ovulatory disorders and women with normal ovulatory cycles.

Relationship of GnRH-stimulated LH release to episodic LH secretion and baseline endocrine-metabolic measures in women with polycystic ovary syndrome.

In polycystic ovary syndrome (PCOS) inappropriate gonadotrophin secretion is characterized by increased pulse frequency and amplitude, elevated 24-h mean serum concentrations, and greater responses to GnRH. While the mechanism(s) responsible for this increased release of LH are not well understood, enhanced LH secretion has been attributed to increased pituitary sensitivity to GnRH and feedback influences from circulating steroid hormones. To address these considerations, we conducted a study to examine the relationships between GnRH-stimulated LH responses, episodic gonadotrophin secretion, and baseline measurements of endocrine-metabolic function in PCOS. Serum LH responses to sequential multidose GnRH administration and pulsatile gonadotrophin secretion were examined in 13 PCOS and 13 normal women. Serum LH, steroid hormone, insulin and glucose levels were determined in blood samples obtained during assessment of episodic gonadotrophin secretion and LH responses to GnRH stimulation. Each subject was studied on two consecutive days. On study day 1 each subject underwent frequent blood sampling every 10 min for 12 h. On study day 2 each received sequential doses of GnRH, 2 microg, 10 microg and 20 microg, administered intravenously at 4-h intervals over a continuous 12-h period. Serum LH responses following GnRH were markedly greater in PCOS compared to normal women, as expected. In individual PCOS, peak LH responses to GnRH were significantly correlated with corresponding basal LH and LH pulse amplitude, but not LH pulse frequency. In the PCOS group, LH responses were positively correlated with serum oestradiol (E2) and inversely related to body mass index (BMI). Between-group differences in LH responsiveness disappeared when controlling for serum testosterone (T) levels. These results indicate that the absolute LH increment following GnRH is largely dependent on baseline LH levels and may account for the well-documented difference in LH responsiveness between PCOS and normal women. That neither LH responses to GnRH nor LH pulse amplitude were correlated to LH pulse frequency suggests involvement of other factors along with GnRH to account for increased LH secretion in PCOS. In addition to E2 and BMI, serum testosterone appears to be, at least in part, responsible for differences in LH secretion and release between PCOS and normal women.

Luteinizing hormone response to controlled-release deslorelin in estradiol benzoate primed ovariectomized gilts

Development of a controlled release formulation of gonadotropin releasing hormone that would stimulate a LH surge capable of reducing the time span of ovulations would greatly benefit reproductive management because a single timed insemination could be used. A dose-response study was conducted to determine if Deslorelin, a potent gonadotropin releasing hormone analogue, delivered via the SABER system, a biodegradable controlled release system, would stimulate an ovulatory-like LH surge in the pig. Twenty ovariectomized gilts, approximately 200 d old and 100 kg body weight (BW), received estradiol benzoate (15 μg/kg BW im) and 48 h later, the gilts were given deslorelin at 0, 12.5, 25.0, 50.0 or 100.0 μg im (n = 4 each treatment group). Compared to controls, mean blood deslorelin concentrations were still elevated at 30 h after deslorelin. Mean deslorelin magnitude, area under the curve and duration were sequentially greater (P<0.05) in a dose-dependent sequence. Compared to controls, serum LH concentrations were elevated (P<0.05) for 6 to 12 h after deslorelin. A dose-response relationship was absent for all parameters of LH secretion. Magnitude of the serum LH response was greatest (P<0.05) in the 12.5 μg and 50.0 μg groups, whereas area under the curve was lower (P<0.05) after 25.0 μg of deslorelin than after 12.5, 50.0 and 100.0 μg, which were not different from each other. Thus, no more than 12.5 μg of deslorelin is necessary to obtain maximum LH release in the model studied and doses less than 12.5 μg may also be effective

Premature elevation in serum insulin-like growth factor-I advances first ovulation in rhesus monkeys.

Previous data suggest that developmental increases in peripheral concentrations of insulin-like growth factor-I (IGF-I) may be one of several neuroendocrine signals that regulate the timing of puberty. In order to test this hypothesis further, normal juvenile female rhesus monkeys (Con; n = 6) were compared with age-matched animals (Igf; n = 4) which received a constant subcutaneous infusion of recombinant human IGF-I (110 micrograms/kg/day) from 18 through 36 months of age. Menstrual bleeding was monitored and ovulation was inferred from a sustained rise in serum progesterone. In order to assess the sensitivity of luteinizing hormone-releasing hormone (LHRH) neurons to excitation, the response of serum LH to the acute administration of the glutamate receptor agonist N-methyl-D, L-aspartic acid (NMDA) was assessed prior to menarche, 2 months following menarche, and during the follicular phase of a female's third ovulation or 50 days after a female's first ovulation. In addition, the pituitary response of LH secretion to an LHRH agonist was assessed during the follicular phase of a female's fourth ovulation or 75 days following her first ovulation. IGF-I treatment effectively elevated serum concentrations by more than 86% of the values observed in Con animals. Although the treatment also enhanced the developmental increase in IGF binding protein-3 (IGFBP-3), IGF-I was increased proportionately more, resulting in a significantly higher molar ratio of IGF-I:IGFBP-3 in treated females throughout the course of the study. Treatment with IGF-I did not affect age at menarche but did significantly advance the age of first ovulation. Consequently, the interval between menarche and first ovulation was significantly shorter in Igf compared with Con females. Although the total number of ovulations exhibited by Igf (3.8 +/- 0.3) and Con females (3.0 +/- 0.5) in the 12 months following menarche was similar, significantly more of these were characterized by normal luteal phase progesterone secretion in Igf (100% +/- 0) compared with Con females (64% +/- 17). An analysis of cycles with a normal luteal phase revealed that serum estradiol during the luteal phase was significantly higher in Igf compared with Con females. Finally, IGF-treated females responded to NMDA treatment with a significantly greater increase in serum LH following menarche but not prior to menarche. In contrast, the response of serum LH to an LHRH agonist did not differ between Igf and Con females. These data suggest that the premature elevation in IGF-I levels, and consequently the ratio of IGF-I:IGFBP-3, accelerates the tempo of the final stages of puberty in rhesus monkeys. This action of IGF-I is probably the result of an increase in LHRH neuronal activity and is not due to a change in pituitary sensitivity to LHRH stimulation. In addition, ovarian sensitivity to LH stimulation during the luteal phase is also increased by IGF-I. Taken together, these data suggest that developmental increases in peripheral IGF-I secretion participate in the neuroendocrine regulation of puberty in female primates.

Inappropriate gonadotropin secretion in polycystic ovary syndrome: influence of adiposity.

In recent years, there has been uncertainty concerning the association of inappropriate gonadotropin secretion (high LH and normal FSH) and the polycystic ovary syndrome (PCOS). In the present study, we ascertained the influence of body composition on LH pulsatile parameters in 33 PCOS and 32 normal cycling (NC) women across a wide range of body mass index (BMI, 19-42 kg/m2). Twenty four-hour pulsatile parameters for serum LH (10-min sampling) and pituitary gonadotropin responses to i.v. bolus GnRH (10 micrograms) were evaluated. Fasting (0800 h) FSH and steroid hormone concentrations and 24-h mean insulin levels were determined. Insulin sensitivity (SI) was assessed by rapid i.v. glucose tolerance test in a subset of 28 PCOS and 29 NC subjects. Our results showed that BMI, an indicator of relative adiposity, had a significant negative impact on 24-h mean LH pulse amplitude (r = -0.63, P < 0.001) and the peak increment of LH in response to GnRH stimulation (r = -0.41; P = 0.02) for PCOS but not NC women. In contrast, 24-h LH pulse frequency was uniformly increased (40%) in PCOS as compared with NC women independent of BMI. In PCOS women, the blunting of pulse amplitude with increasing BMI resulted in a decline in 24-h mean LH levels (r = -0.63, P < 0.001) and the ratio of LH/FSH (r = -0.44, P = 0.02) not seen in NC. With BMI < 30 kg/m2, 24-h mean LH values for PCOS women were greater than the normal range for NC in 95% (18/19) of cases, whereas 24-h LH levels failed to discriminate PCOS from NC women in 43% (6/14) of obese (BMI > 30 kg/m2) PCOS women. Thus, the diagnostic value of LH determinations is retained for PCOS women with BMI < 30 kg/m2. For screening purposes, the mean of two LH values in samples collected at 30-min intervals was found to have a discriminatory power equal to that of the 24-h mean. These findings suggest that 1) BMI negatively influences LH pulse amplitude in PCOS women principally by an effect at the pituitary level; 2) accelerated LH pulse frequency in PCOS women is not influenced by BMI and represents a basic component of hypothalamic dysfunction in PCOS women; and 3) BMI does not influence gonadotropin secretion in normal cycling women. Thus assessments of basal LH levels and the LH/FSH ratio in hyperandrogenic anovulatory women are clinically meaningful when BMI is taken into account. Investigations to define the factor(s) that link adiposity and the attenuation of LH pulse amplitude in PCOS women would add further understanding of this complex neuroendocrine-metabolic disorder.

Menstrual Cyclicity After Metformin Therapy in Polycystic Ovary Syndrome

Objective: To assess the effect of insulin-lowering treatment on menstrual cyclicity in polycystic ovary syndrome (PCOS).Methods: Forty oligoamenorrheic women with PCOS were recruited in a prospective clinical study to receive metformin for a minimum period of 6 months. Twenty-two women completed the study. Serum LH, FSH, free testosterone, and glucose and insulin response to oral glucose load were measured both before and after 8 weeks of metformin treatment. Menstrual cyclicity and serum progesterone levels at the midluteal phase were assessed at the 30th week of metformin treatment.Results: Twenty-one of 22 women had restoration of menstrual cyclicity (95.7%). Four of these women (19%) became pregnant within the 6th and 7th months of treatment. All four of the pregnant women delivered, and the infants were healthy. Thirteen of 15 women who had regular menses demonstrated a serum progesterone level within the ovulatory range (3.1–28 ng/mL). Fasting (P < .001) and the integrated insulin response to the glucose load decreased (P < .001) after 8 weeks of metformin treatment. This was accompanied by significant decreases in serum LH (P < .001) and free testosterone (P < .001) levels and LH/FSH ratio (P < .001). There was a small but significant reduction in body mass index after 8 weeks of metformin treatment (P < .001).Conclusion: A 6-month course of metformin may improve menstrual cyclicity and fertility in women with the PCOS. Insulin-sensitizing agents provide a rational approach to the treatment of the metabolic and endocrine abnormalities in PCOS women.

EVALUATION OF HYPOTHALAMIC-PITUITARY-GONADAL (HPG) FUNCTION IN PATIENTS WITH TURNER SYNDROME (TS) WITH THE GnRH ANALOG (GnRHa) SUBACUTE TEST

We have previously described that a GnRH test (100 ug of SC Buserelin acetate administered twice at a 24 hs interval) can be used to evaluate the HPG axis in normal prepubertal girls (J Pediat 122:46,1993). In order to evaluate ovarian steroidogenic capacity and the role of sex steroids (SS) in the regulation of pituitary gonadotropins LH and FSH at late prepuberty (Pre), a GnRHa test was carried on in 14 girls with TS and bone ages (BA) between 6.16 and 12 years (y). Serum LH, FSH and E2 was evaluated in basal (B) conditions. 24 hs after the first and 4, 6 and 24 hs after the second injection of Buserelin. A positive response of serum E2 (E2≥55 pmol/L) was only detected in 4 patients. To evaluate LH and FSH responses, patients were divided into 2 groups (Gr) as a function of E2 response: Gr1(E2 ≥55pmol/L), mean±SD chronological age (CA) 9.94±1.84 y and BA 7.41±1.33 y and Gr2 (E2 <55pmol/L, n=10), CA 11.5±3.34 y and BA 9.97±2.49 y. BA was similar in the two groups. B LH and FSH in Gr1 was significantly lower than in Gr2: Median(M) LH was 0.31 (r:0.15-0.49) and 6.79 (r:0.1-54.1) while M FSH was 12.5(r:8.07-17.5) and 43.8(r:8.81-135) U/L, respectively, p<0.05 Dunn's test. Serum LH response to GnRHa was significantly different between Gr1 and Gr2 only 24 hs after the second stimulation (median 1.09, r:0.31-6.6 and 5.1, r:1.21-58, respectively, p<0.05). FSH was similar in the two groups at every sampling time. Conclusions: 1) the GnRHa test in TS is useful to evaluate the steroidogenic capacity of the ovary, 2) lack of difference in FSH response to GnRHa in the two groups would suggest similar ovarian inhibin deficiency, and 3) the differences between Gr1 and Gr2 in B LH and in LH 24 hs after the second GnRHa stimulation suggest that ovarian SS play a role in the regulation of LH secretion in late prepuberty as well as in early puberty.

Metabolic changes during the transition from the fed to the acute feed-deprived state in prepuberal and mature gilts.

The present study compared the metabolic response to acute feed deprivation in ovariectomized prepuberal (P; n = 6), 62 +/- 2 kg BW, and mature (M; n = 6) gilts, 124 +/- 4 kg BW. Blood was collected at 1, 2, 3, 4, 6, 8, 12, 16, 20, 24, 28, 32, 40, and 48 h after initiation of feeding. Samples were quantified for glucose, insulin, free fatty acids (FFA), beta-hydroxybutyrate (HBA), IGF-I, IGF binding proteins (BP)-1 to -4, cortisol, and amino acids (AA). At 24 h, blood samples were collected every 15 min for 8 h and an additional 1 h after i.v. injection of GnRH (.2 microgram/kg BW) and growth hormone-releasing factor (GRF; 1 microgram/kg BW). Samples were assayed for growth hormone (GH) and LH. Serum insulin concentrations were lower (P < .05) in P gilts. Plasma glucose concentrations were similar. Serum FFA concentrations were greater (P < .05) in P gilts. Serum concentrations of HBA were greater (P < .001) in P gilts at 48 h. Serum IGF-I concentrations were lower (P < .05) in P gilts by 16 h. Serum IGFBP-1-4 levels were similar. Serum cortisol concentrations were similar. Serum concentrations of the essential AA, isoleucine, lysine, threonine, valine, and phenylalanine were greater (P < .05) in P gilts at 40 h. Serum LH concentrations and response to GnRH were similar. Basal serum GH concentrations and peak response to GRF were greater (P < .05) in P than in M gilts. The transition from fed to unfed state occurs more rapidly in P than in M gilts.

Effect of dietary zinc deficiency on reproductive function in male rats: Biochemical and morphometric parameters

The effect of zinc on reproductive function was studied in rats fed with a zinc-deficient diet and control rats fed with a standard diet. Serum testosterone (T) levels were measured before and after the injection of HCG (human chorionic gonadotropin). Serum gonadotrophin levels were measured before and after the injection of GnRH (gonadotropin releasing hormone). In addition, structural parameters were studied and morphometric techniques were used to study the seminiferous tubules. The findings were used to investigate the possible relationship between biochemical and morphometric changes. Body weight (BW) gain, zinc content of testes and weight of the testes, seminal vesicle, and prostate were significantly lower in zinc-deficient rats compared with controls. Serum zinc concentrations and alkaline phosphatase activity were decreased in zinc-deficient rats compared with controls. Serum basal and stimulated FSH concentrations were similar in the two groups. Serum LH response to GnRH was higher in zinc-deficient rats. Serum basal T was lower in zinc deficient animals, but the response of T to HCG was similar in the two groups. The basal and luminal diameters, perimeter, and surface area of the seminiferous tubules as well as tubule volume, wall thickness, and cross-section area decreased in zinc-deficient animals in comparison with controls. Concentrations of zinc were significantly correlated with structural parameters and serum T levels. The changes in T levels correlated positively with the structural parameters and morphological findings.

Response of serum LH and milk progesterone to two GnRH agonists, fertirelin and buserelin, in cows with ovarian follicular cysts

Follicular cysts were diagnosed in 172 Holstein cows by rectal palpation, and the diagnosis was confirmed in 41.3% of the cows, using 3 consecutive milk progesterone tests. For 57 cows with cysts, treated with 200 μg fertirelin or 20 μg buserelin 14 days after first examination, the average serum LH concentration 2.0-2.5 h after treatment was 22.5 and 20.6 ng/ml respectively, and luteinization occurred in 76.7 and 66.7% of cows. Of cows treated with fertirelin and buserelin, 75 and 72% respectively showed an increase in milk progesterone to ?1.0 ng/ml. The percentage of cows conceiving within 180 days of treatment was 70.8 and 61.9% respectively in the 2 groups, and the service period averaged 71±41 and 63±53 days respectively. The differences between treatments were not significant.

Oestradiol negative feedback inhibition on LH secretion during lactation is prolonged in adolescent primiparous rhesus monkeys

Lactational infertility in rhesus monkeys is significantly prolonged in adolescent primiparous compared with adult multiparous mothers. In order to determine if this longer period of infertility for young mothers is the result of a greater sensitivity to nursing-induced inhibition of LH release either by enhanced oestradiol negative feedback or a direct non-gonadally mediated suppression, the effects of periodic administration of oestradiol on serum LH concentrations in nursing ovariectomized adolescent primiparous (Prp; n = 5) and adult multiparous (Mlt; n = 7) mothers was assessed. Females were treated every 5-6 weeks with a 21-day time-release capsule of oestradiol which produced serum concentrations of approximately 250, 90 and 45 pmol/l by +6, +13 and +20 days after treatment. Thus, the design permitted assessment of LH and prolactin concentrations under a regime of 21 days of decreasing oestradiol levels followed by 2-3 weeks of no oestradiol treatment. Females were studied from week 3 to week 42 post partum and oestradiol treatment occurred during weeks 5, 11, 21, 26, 31, 36 and 41. Behavioural observations indicated that the amount of time mothers nursed their offspring decreased in a similar fashion throughout the lactational period for both Prp and Mlt females. LH concentrations under the 'no oestradiol' conditions progressively increased throughout lactation reaching maximum levels by week 36 post partum in a similar manner for both Prp and Mlt mothers. These data suggest that differences in fertility between adolescent and adult nursing mothers observed previously cannot be attributed to a difference in a direct non-gonadally-mediated affect on LH. With respect to oestradiol negative feedback inhibition of LH, oestradiol treatment effectively suppressed serum LH concentrations at all points during lactation up to week 31, at which time LH concentrations were maximally suppressed in both Prp and Mlt mothers at +6 days after treatment but by day +13 LH values were significantly higher in Mlt females. After oestradiol treatment during week 36, LH values were again maximally suppressed on day +6 in Prp females but not in Mlt females. However, the response of serum LH after oestradiol treatment during week 41 was similar between Prp and Mlt females at all sampling points.(ABSTRACT TRUNCATED AT 400 WORDS)

Dexamethasone Alters Responses of Pituitary Gonadotropin-Releasing Hormone (GnRH) Receptors, Gonadotropin Subunit Messenger Ribonucleic Acids, and Gonadotropins to Pulsatile GnRH in Male Rats*

Dexamethasone (Dex), when administered in high doses, has been shown to suppress spontaneous and GnRH-induced gonadotropin secretion, but the level and the mechanism(s) of this effect are unknown. We administered Dex to castrate testosterone-replaced male rats to determine if gonadotropin gene expression is affected and whether Dex differentially influences GnRH-modulated parameters of gonadotrope function: induction of GnRH receptors (GnRH-R) and gonadotropin synthesis and secretion. GnRH was given iv at 25 ng/pulse at 8, 30, and 120 min intervals for 48 h. Rapid GnRH injection frequency preferentially increased alpha and LH-beta messenger RNA (mRNA) responses to GnRH as well as LH secretion. Slower GnRH injection frequencies were required to increase levels of GnRH-R, FSH-beta mRNA, and FSH secretion. Dex selectively inhibited the serum LH, alpha, and LH-beta mRNA responses to GnRH, but not the serum FSH or FSH-beta mRNA responses. Additionally, it augmented the GnRH-induced increase in GnRH-R. We conclude: 1) induction of GnRH-R, gonadotropin synthesis, and secretion require different modes of GnRH stimulation; 2) Dex acts directly on the gonadotrope to differentially modulate GnRH-induced increases in GnRH-R levels, gonadotropin gene expression, and gonadotropin secretion; and 3) GnRH effects upon induction of GnRH-R, LH, and FSH synthesis and secretion are likely to be mediated via different cellular pathways.

Dopaminergic Control of Gonadotropin Secretion in Male Senescence

To verify the role of the dopaminergic mechanism in the control of gonadotropin secretion and aging of this mechanism in men, we studied serum gonadotropin response to LH-RH (100 micrograms i.v.) in basal condition and during dopamine infusion (DA 4 micrograms/kg/min). Seven young males (24-29yr.) and twenty aged males (50-80yr.) without endocrinological diseases were included in the present study. Aged male subjects were divided into hyperresponders, in whom maximal LH response to LH-RH without DA infusion exceeded 153.5mIU/ml (mean + 2SD of young male subjects), and non-hyperresponders, in whom maximal LH responses to LH-RH without DA infusion were less than 153.5mIU/ml. In hyperresponders, serum LH response at 30 minutes after LH-RH administration was significantly (p less than 0.05) suppressed by DA infusion. In non-hyperresponders and young male subjects, however, serum LH response to LH-RH was not affected by DA infusion. Basal levels of serum LH and FSH in hyperresponders tended to be higher than that of non-hyperresponders. Total serum testosterone, free testosterone and estradiol levels of hyper and non-hyperresponders failed to reveal any significant differences. These observations suggest that 1) DA directly suppresses gonadotroph responsiveness to LH-RH, 2) in aging men, inhibitory tone imposed on gonadotrophs by DA is decreased, and 3) this decline of DA system can cause hypergonadotropism in aging men, independent of serum sex steroids levels.

Hypothalamic-Pituitary-Ovarian Function in Menstruating Women with Turner Syndrome (45,X)

The hypothalamic-pituitary-ovarian hormone secretion patterns were evaluated in two women with 45,X Turner syndrome, spontaneous sexual development, and monthly menstrual periods. Each women had serum gonadotropin and sex steroid determinations during two or more menstrual cycles. During the follicular phase of a menstrual cycle, both women received 100 micrograms gonadotropin-releasing hormone (GnRH) s.c., and serum LH and FSH responses were determined. In addition, one woman collected daily overnight urine specimens for 40 consecutive days, spanning two menstrual periods, for the measurement of LH, FSH, estriol, and free progesterone. The randomly measured hormone results showed low serum progesterone concentrations during luteal phases, consistent with the interpretation of anovulation or inadequate corpus luteum function. At the time of the GnRH stimulation tests, baseline serum FSH concentrations and FSH responses to GnRH were within normal limits, whereas baseline LH levels and LH responses to GnRH were low. The pituitary gonadotropin secretion patterns were more consistent with patterns seen during early puberty than in the perimenopausal state. This interpretation was further confirmed by the urinary excretion patterns of gonadotropins, which were not significantly elevated. Furthermore, the urinary hormone profiles revealed that, although the intermenstrual period was of normal length, the follicular phase was prolonged, with normal levels of LH, FSH, and estriol excreted. The menstrual cycle studied was ovulatory but had a short luteal phase. The hormone results indicated that the dysgenetic ovary of women with 45,X Turner syndrome is capable of producing sufficient quantities of sex steroids and other regulatory factors to maintain gonadotropin secretion patterns that are reminiscent of early puberty.(ABSTRACT TRUNCATED AT 250 WORDS)

Combined anterior pituitary function test using CRH, GRH, LH-RH, TRH and vasopressin in patients with non-functioning pituitary tumors.

We examined 8 normal subjects and 16 patients with non-functioning pituitary tumors with a combined anterior pituitary test to evaluate the clinical usefulness of the test. Diagnoses included 9 of chromophobe adenoma, 3 of craniopharyngioma, 2 of Rathke's cleft cyst, and 1 each of intrasellar cyst and tuberculum sella meningioma. All subjects received hypothalamic releasing hormones: 1 micrograms/kg corticotropin releasing hormone (CRH), 1 micrograms/kg growth hormone releasing hormone (GRH), 500 micrograms thyrotropin-releasing hormone (TRH), 100 micrograms luteinizing hormone releasing hormone (LH-RH), and a relatively small dose (5 mU/kg) of lysine vasopressin (LVP). In the normal subjects, the addition of LVP potentiated the secretion of adenocorticotropic hormone (ACTH) induced by CRH, but had no significant effect on the secretion of other anterior pituitary hormones. In the combined test with 5 releasing hormones, the plasma ACTH and cortisol responses were not impaired in the majority of the patients before pituitary surgery. Serum thyroid-stimulating hormone (TSH), prolactin (PRL) and follicle-stimulating hormone (FSH) responses were not impaired in 82%, 70% and 67% of the patients, respectively, while the serum LH and GH responses were impaired in 67% and 73% of the patients, respectively. Following pituitary surgery, responses of these hormones to combined testing were similarly impaired in more than 75% of the patients. These results indicate that plasma ACTH, cortisol and serum TSH responses are fairly good before pituitary surgery but are impaired significantly after surgery. No subjects experienced any serious adverse effects related to the testing. These results suggest that combined testing with hypothalamic hormones is a convenient and useful method for evaluating pituitary function.

Regulation of LH.BETA. Subunit mRNA in Immature Female Rats during GnRH Agonist Treatment.

In order to determine the changes in the expression of LH beta messenger ribonucleic acid (mRNA) during GnRH agonist (GnRHa) treatment (0.94 mg/28 days), the concentration of the mRNA of LH beta was assessed together with the serum LH concentration, pituitary LH content and LH response to GnRH at various times during long-acting GnRHa treatment in immature female rats. The serum LH concentration was increased at hour 1, gradually decreased starting at approximately hour 3 and had returned to the control level on day 28. Pituitary LH began to decrease at hour 3. The concentrations of LH beta mRNA were not significantly different from those in the control group from hour 1 to hour 18, but were lower from day 3 to day 28. Serum LH response to native GnRH (1 micrograms) began to be inhibited on day 7. These results indicate that the short term treatment with GnRHa stimulates the release of preformed LH rather than synthesis of LH beta mRNA and that the long term treatment inhibited the expression of LH beta mRNA in a time dependent manner.

DEPOT LEUPROLTDE ACETATE FOR TREATMENT OF PRECOCIOUS PUBERTY

Leuprolide acetate (D-Leu 6 des-Gly-NH2(10), Pro-ethylamide9) for depot suspension has been shown to be effective in suppressing gonadotropins in 6 patients. Serum LH and FSH response to exogenous LHRH was obliterated after 4 weeks and weekly urinary gonadotropin levels during depot therapy were suppressed. This form of this drug should be effective in the treatment of precocious puberty.