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Biomedical subjects

W F Crowley

Publications and source records attributed to W F Crowley.

At least 109 records · Page 6Linked to original sources
PubMed1991

Altered patterns of pituitary secretion and renal excretion of free alpha-subunit during gonadotropin-releasing hormone agonist-induced pituitary desensitization.

Intact LH and free alpha-subunit (FAS) are differentially regulated during GnRH agonist (GnRHa)-induced pituitary desensitization; circulating levels of FAS rise, while LH levels decline. Increased steady state alpha and decreased LH beta mRNA levels in desensitized rat pituitaries suggest that differential regulation occurs at the level of subunit transcription. We assessed a renal contribution to these changes in serum hormone concentrations by studying LH and FAS levels in serum and urine in 15 pubertal children before and during long term GnRHa administration. Before GnRHa, serum LH and FAS were secreted in concordant pulses, and both responded briskly to exogenous GnRH. During GnRHa-induced pituitary desensitization, mean (+/- SEM) serum and urinary LH levels fell [11 +/- 3 vs. 2 +/- 0.2 IU/L (P less than 0.01) and 39 +/- 15 vs. 5 +/- 1 IU/g creatinine (P less than 0.05), respectively), and the LH response to exogenous GnRH was ablated (117 +/- 20 vs. 1 +/- 0.3 IU/L; P less than 0.01). In contrast, despite suppression of FAS pulsatility, mean serum FAS levels rose during GnRHa treatment (204 +/- 23 vs. 405 +/- 50 ng/L; P less than 0.01), and responsiveness to exogenous GnRH was maintained. Paradoxically, urinary FAS levels fell (3.2 +/- 0.9 vs. 1.7 +/- 0.4 micrograms/g creatinine; P less than 0.05) as did its renal clearance (3.1 +/- 0.5 vs. 1.3 +/- 0.1 mL/min.m2; P less than 0.05). We conclude that during GnRHa-induced pituitary desensitization, the gonadotrope maintains the ability to respond to GnRH with FAS release, and the rise in serum FAS is due in part to its diminished renal clearance.

Adolescent↗
PubMed1991

Variable tolerance of the developing follicle and corpus luteum to gonadotropin-releasing hormone antagonist-induced gonadotropin withdrawal in the human.

To examine the differential sensitivity of the ovary to temporary withdrawal of gonadotropin support at different stages of folliculogenesis and corpus luteum function, GnRH antagonist blockade of gonadotropin secretion was examined in 17 studies using the Nal-Glu GnRH antagonist. A vehicle control, antagonist treatment, and follow-up cycle format was used in each study. A previously determined ED100 dose of the Nal-Glu GnRH antagonist (150 micrograms/kg) or vehicle was administered sc every 24 h for 3 consecutive days in the midfollicular phase (MFP), late follicular phase (LFP), and midluteal phase (MLP). In studies in the MFP (n = 7), the largest follicle was 11 +/- 2 mm (mean +/- SEM), and the mean estradiol (E2) level was 220 +/- 44 pmol/L on the first day of antagonist administration. Administration of the antagonist resulted in a 75 +/- 6% suppression of LH (P less than 0.005), no significant change in FSH, and suppression of E2 to the assay detection limit (P less than 0.05). Total cycle length was increased compared to that of the vehicle control cycle (37.3 +/- 1.3 vs. 26.3 +/- 1.1 days; (P less than 0.005) due to prolongation of follicular phase length (P less than 0.005) and reinitiation of folliculogenesis. In the LFP (n = 5), the largest follicle was 16 +/- 1 mm (P less than 0.05 vs. MFP), and the E2 level was 394 +/- 95 pmol/L (P less than 0.05 vs. MFP) on the first day of antagonist administration. Antagonist administration resulted in a 65 +/- 6% suppression of LH (P less than 0.05), a 47 +/- 11% decrease in FSH (P less than 0.05), and no significant change in E2. Total cycle length was prolonged (32.4 +/- 2.2 vs. 25.6 +/- 0.4 days; P less than 0.05) due to an increase in follicular phase length (P less than 0.02); however, the prolongation of the follicular phase was significantly less than that of the MFP (8.0 +/- 1.5 vs. 15.1 +/- 0.1 days; P less than 0.001), suggesting ovulation from the initial dominant follicle. In studies in the MLP (n = 5), LH, E2, and progesterone decreased to the assay detection limit after antagonist administration, while FSH decreased by 36 +/- 4% (P less than 0.05). Menstrual bleeding occurred within 24-48 h of the final Nal-Glu antagonist injection.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1991

Sex steroid control of gonadotropin secretion in the human male. I. Effects of testosterone administration in normal and gonadotropin-releasing hormone-deficient men.

The precise sites of action of the negative feed-back effects of gonadal steroids in men remain unclear. To determine whether testosterone (T) administration can suppress gonadotropin secretion directly at the level of the pituitary, the pituitary responses to physiological doses of GnRH were assessed in six men with complete GnRH deficiency, whose pituitary-gonadal function had been normalized with long term pulsatile GnRH delivery, before and during a 4-day continuous T infusion (15 mg/day). Their responses were compared with the effects of identical T infusions on spontaneous gonadotropin secretion and the response to a 100-micrograms GnRH bolus in six normal men. Both groups were monitored with 15 h of frequent blood sampling before and during the last day of the T infusion. In the GnRH-deficient men, the first three GnRH doses were identical and were chosen to produce LH pulses with amplitudes in the midphysiological range of our normal men (i.e. a physiological dose), while the last four doses spanned 1.5 log orders (7.5, 25, 75, and 250 ng/kg). The 250 ng/kg dose was always administered last because it is known to be pharmacological. In the GnRH-deficient men, mean LH (P less than 0.02) and FSH (P less than 0.01) levels as well as LH pulse amplitude (P less than 0.05) decreased significantly during T infusion, demonstrating a direct pituitary-suppressive effect of T and/or its metabolites. Mean LH levels were suppressed to a greater extent in the normal than in the GnRH-deficient men (58 +/- 15% vs. 28 +/- 7%; P less than 0.05). In addition, LH frequency decreased significantly (P less than 0.01) during T administration in the normal men. These latter two findings suggest that T administration also suppresses hypothalamic GnRH release. T was unable to suppress gonadotropin secretion in one GnRH-deficient and one normal man. In both groups, the suppressive effect of T administration was present only in response to physiological doses of GnRH. Because the pituitary- and hypothalamus-suppressive effects of T could be mediated by its aromatization to estrogens, five GnRH-deficient and five normal men underwent identical T infusions with concomitant administration of the aromatase inhibitor testolactone (TL; 500 mg, orally, every 6 h). As an additional control, four GnRH-deficient and four normal men received TL alone. TL administration completely prevented the effect of T administration to suppress gonadotropin secretion in both the normal and GnRH-deficient men, and mean LH levels increased significantly in both the GnRH-deficient (P less than 0.01) and the normal (P less than 0.001) men who received TL alone. The increase in mean LH levels was greater (P less than 0.01) in the normal men who received TL alone than in the normal men who received T plus TL, thus revealing a direct effect of androgens in normal men. Measurements of T and estradiol production rates in three men demonstrated that TL effectively blocked aromatization.(ABSTRACT TRUNCATED AT 400 WORDS)

Administration, Oral↗
PubMed1991

Sex steroid control of gonadotropin secretion in the human male. II. Effects of estradiol administration in normal and gonadotropin-releasing hormone-deficient men.

Although prior studies have suggested that estrogens exert their negative feedback effect at the pituitary level in men, these conclusions have been based on models that evaluate changes in LH pulse amplitude and frequency and, therefore, only provide indirect information concerning the site of action of estrogens. To assess whether estradiol (E2) inhibits gonadotropin secretion directly and solely at the pituitary level in men, we determined the pituitary responses to physiological doses of GnRH in six men with complete GnRH deficiency, whose pituitary-gonadal function had been normalized with long term pulsatile GnRH delivery, before and during a 4-day continuous E2 infusion (90 micrograms/day). To deduce whether E2 has an additional inhibitory effect on hypothalamic GnRH secretion, their responses were compared with the effects of identical E2 infusions on spontaneous gonadotropin secretion and the responses to a 100-micrograms GnRH bolus in six normal men. Both groups were monitored with 15 h of frequent blood sampling before and during the last day of the E2 infusion. In the GnRH-deficient men, the first three GnRH doses were identical and chosen to produce LH pulses with amplitudes in the midphysiological range of values in our normal men (i.e. a physiological dose), while the last four doses spanned 1.5 log orders (7.5, 25, 75, and 250 ng/kg). The 250-ng/kg dose was always administered last because it is known to be pharmacological. In the GnRH-deficient men, mean LH and FSH levels as well as LH pulse amplitude all decreased significantly (P less than 0.02) during E2 infusion, demonstrating a direct pituitary-suppressive effect of E2. Mean LH (P less than 0.01) and FSH (P less than 0.05) levels and LH pulse amplitude (P less than 0.01) also decreased significantly in the normal men. The degree of suppression of mean LH (52 +/- 3% vs. 42 +/- 12%) and FSH (49 +/- 10% vs. 37 +/- 10%) levels was similar in the two groups. These results provide direct evidence that E2 inhibits gonadotropin secretion at the pituitary level in men and suggest that the pituitary is the most important, and possibly the sole, site of negative feedback of estrogens in men.

Adult↗
PubMed1991

Serum melatonin in central precocious puberty is lower than in age-matched prepubertal children.

In children a progressive decrease in nocturnal serum melatonin (MT) has been shown with advancing age, suggesting a reduction in the amplitude of the circadian MT curve with maturation. Whether this alteration of MT levels is related to human sexual maturation or occurs independently remains to be elucidated. Also, the impact of gonadal steroids on the MT rhythm remains an open question. We examined 56 patients (51 females and 5 males) with central precocious puberty (52 idiopathic and 4 neurogenic). Patients were studied before and 3, 6, and 12 months after initiation of GnRH analog treatment. Three hundred and thirty-seven endocrinologically normal subjects (190 males and 147 females) served as controls. In all subjects nocturnal serum MT (blood collection between 2300 and 0100 h) was measured with a highly specific RIA. In young patients, aged 1-5 yr, we found significantly lower MT levels than in age-matched controls. Pubertal patients, aged 5-9 yr, displayed nocturnal MT levels in the same range as control subjects approaching normal pubertal age. In contrast to endocrinologically normal children, there was no age-dependent decrease in nocturnal MT in untreated precocious puberty; rather, it appeared that serum MT had already declined in association with the onset of sexual maturation. Although there was a significant difference in weight between patients and age-matched controls, the low MT values in patients 1-5 yr old were only partly explained by the weight difference (P less than 0.0009); their pubertal status also contributed significantly (P less than 0.006). Pituitary-gonadal suppression induced by long term GnRH analog treatment did not result in a return to prepubertal MT levels; rather, nocturnal MT decreased during therapy. The collected data indicate that nocturnal serum MT levels are related to sexual maturation, since serum MT is similar in precocious puberty and normal pubertal children. Since suppression of the pituitary-gonadal axis did not result in increases in nocturnal MT levels in young patients with precocity (i.e. return to age-appropriate levels), the reduction of nocturnal MT with normal puberty is not likely to be dependent on pubertal gonadotropin or sex steroid milieu.

Aging↗
PubMed1991

Development of a radioligand receptor assay for measuring follitropin in serum: application to premature ovarian failure.

We have developed a radioligand receptor assay (RRA) with sufficient sensitivity and specificity for quantifying follitropin (FSH) in unextracted serum samples. Standard curves prepared by adding pituitary FSH to either buffer or gonadotropin-free serum were parallel and statistically indistinguishable in this assay, whereas gonadotropin-free serum alone had no activity. Cross-reactivity with related pituitary hormones was negligible. Pituitary FSH was calibrated with commonly used reference preparations so that RRA results could be compared with RIA results for identical standards. The patterns in daily blood samples in six normal menstrual cycles were similar by both methods. The mean RIA:RIA ratio in both the follicular and luteal phases was between 0.6 and 0.7, and at mid-cycle decreased to 0.48, suggesting an alteration of isohormone composition at mid-cycle. In 27 women with premature ovarian failure, RRA:RIA ratios ranged from below the RRA minimum detectable dose to 4.6, suggesting that immunoreactive FSH might not be capable of binding to the FSH receptor in some patients, whereas in patients with high RRA:RIA ratios, circulating inhibitors of FSH receptor binding might be present and perhaps contributing to the observed ovarian failure. Use of this RRA in conjunction with RIA and in vitro bioassays may better define the relative contribution of FSH isohormones, autocrine or paracrine modulators of FSH bioactivity, and FSH-receptor binding competitors to the "total FSH biological signal" as detected by the gonadal FSH receptor.

Adult↗
PubMed1990

Gonadotropin-releasing hormone deficiency in men: diagnosis and treatment with exogenous gonadotropin-releasing hormone.

Idiopathic hypogonadotropic hypogonadism in men is the result of absent or abnormal secretion of gonadotropin-releasing hormone, which prevents pubertal development. Isolated gonadotropin-releasing hormone deficiency is clinically and neuroendocrinologically heterogeneous, largely because of variation in the degree of gonadotropin-releasing hormone deficiency. Treatment with pulsatile gonadotropin-releasing hormone results in normal pubertal changes and virilization. Such treatment has been uniformly successful in normalizing release of gonadotropins and secretion of testosterone. Improvement in secondary sex characteristics and induction of spermatogenesis have been achieved in most patients. Eight of nine patients desiring induction of fertility were able to father a child. Use of pulsatile gonadotropin-releasing hormone presents a powerful model in which to examine regulation of gonadotropin secretion and the role of hypothalamic gonadotropin-releasing hormone in control of the male reproductive axis.

Adolescent↗
PubMed1990

An improved method of purifying inhibin radioligand for radioimmunoassay.

Polyacrylamide gel electrophoresis (PAGE) separation of bovine inhibin from free iodine after iodination is described. Previous methods of separation typically relied upon a G25 gel filtration and Matrix gel Red A affinity column chromatography protocol. When compared to column chromatography, PAGE-purified radiolabelled inhibin resulted in significantly increased binding (13.1% vs. 7.5%) and enhanced sensitivity (ED50 = 92 microliters inhibin standard vs. ED50 = 198 microliters inhibin standard) to the inhibin antibody #1989. Our results demonstrate an advantageous approach to purifying 31,000 Mr bovine inhibin radioligand after iodination for RIA.

Chromatography, Ion Exchange↗
PubMed1990

Gonadotrophin-releasing hormone agonist treatment of central precocious puberty: an analysis of growth data in a developmental context.

Growth and skeletal maturation was assessed in 83 girls with central precocious puberty (CPP) during pituitary-gonadal suppression induced by treatment with a gonadotrophin-releasing hormone agonist (GnRHa). The mean pretreatment chronological age (CA) was 6.3 years and the mean bone age (BA) was 10.6 years. During the suppression of gonadal sex steroid secretion, mean height velocity (HV) decreased from a pretreatment value of 10.8 cm/year to 5.9 (year 1, n = 83), 4.9 (year 2, n = 72), 4.2 (year 3, n = 45), and 4.4 (year 4, n = 23) cm/year. During each interval, there was a negative correlation between HV and the pretreatment BA. In addition, the rate of skeletal maturation was reduced during GnRHa treatment (delta BA/delta CA = 0.6 +/- 0.1 over 3 years, n = 45). The rate of skeletal maturation during therapy was also negatively correlated with pretreatment BA. Predicted adult stature, based upon zeta-scores of height for BA, increased significantly and progressively during therapy but the changes in height SDS for BA varied significantly. Since HV, delta BA/delta CA, and the change in height SDS for BA (delta HT SDS for BA) during pituitary-gonadal suppression all correlated with the initial degree of skeletal maturation, the effect of GnRHa therapy on final adult height in children with CPP will be best understood if growth data are assessed within a developmental framework.

Age Factors↗
PubMed1990

Gonadotropin-releasing hormone-induced stimulation and desensitization of free alpha-subunit secretion mirrors luteinizing hormone and follicle-stimulating hormone in perifused rat pituitary cells.

A pulsatile pattern of hypothalamic GnRH stimulation is necessary for the maintenance of pituitary LH and FSH secretion, with continuous GnRH leading to a decrement in response. Although the physiological pattern of free alpha-subunit secretion closely mimics that of LH, several reports have indicated that free alpha-subunit is not desensitized by continuous GnRH stimulation. To explore the basis of this phenomenon, we have evaluated the responses of all three gonadotrope secretory products to carefully coordinated administration of pulsatile and continuous GnRH in a dispersed rat pituitary perifusion system. Sensitivities (ED50) to GnRH fell within a narrow range for free alpha-subunit (11.5 nM), LH (12.9 nM), and FSH (17.3 nM), although a greater mass of LH than free alpha-subunit or FSH was released after each pulse of GnRH. The response to a standard GnRH pulse (10 nM) administered every 15, 30, or 120 min for 9 h was very stable, with no evidence of priming, summation, or loss of response. LH, FSH, and free alpha-subunit did, however, show significantly (P less than 0.05) higher pulse amplitude with longer interpulse intervals. In contrast to previous observations in vivo, the three gonadotrope secretory products showed parallel desensitization in response to continuous infusions of GnRH. This loss of response was significant (P less than 0.05) after exposure to as little as 0.1 (FSH) to 0.5 nM (LH and alpha-subunit) GnRH for 2 h or to higher concentrations of GnRH (10 nM) for as little as 15 min (LH, FSH, and alpha-subunit). These concentrations and durations of GnRH stimulation are within the range of values measured in vivo. We conclude that 1) free alpha-subunit, LH, and FSH have similar concentration and frequency responses to pulsatile GnRH, although the absolute amount of hormone released is different for each secretory product; 2) the frequency of pulsatile GnRH stimulation can function as an independent determinant of secretion for each of the three products; and 3) in contrast to observations in vivo, free alpha-subunit, LH, and FSH secretion desensitize similarly after exposure to concentrations or durations of GnRH that may occur in vivo. These observations raise the possibility that desensitization plays a role in the physiological regulation of gonadotrope secretion.

Animals↗
PubMed1990

Differential regulation of luteinizing hormone, follicle-stimulating hormone, and free alpha-subunit secretion from the gonadotrope by gonadotropin-releasing hormone (GnRH): evidence from the use of two GnRH antagonists.

To examine the differential regulation of glycoprotein hormone secretion from the gonadotrope by GnRH, the Nal-Glu GnRH antagonist was administered to euthyroid women in the early follicular phase (days 1-5) of the menstrual cycle, and the results compared to previous studies with the Nal-Arg GnRH antagonist. After a 4-h period of baseline sampling at a frequency of every 10 min, a single sc dose of the GnRH antagonist was administered to each subject. Frequent sampling continued for 8 h, followed by hourly sampling for a further 16 h. LH, FSH, and free alpha-subunit were measured serially in assays with high specificity. There was a 90% concordance of LH and free alpha-subunit pulses during the baseline sampling period. Pulsatile secretion of LH and free alpha-subunit was immediately abolished at the highest dose of the Nal-Glu antagonist for at least 8 h. The maximum percent suppression of LH after administration of the Nal-Glu GnRH antagonist was 70 +/- 4%, 80 +/- 4%, and 83 +/- 1% at doses of 15, 50, and 150 micrograms/kg, respectively, compared to 51 +/- 10%, 70 +/- 5%, and 69 +/- 5% at doses of 50, 150, and 500 micrograms/kg Nal-Arg antagonist. Decreases in FSH were 28 +/- 2%, 32 +/- 7%, and 39 +/- 2%, with increasing doses of the Nal-Glu antagonist compared with 25 +/- 6%, 17 +/- 6%, and 28 +/- 4% reductions at increasing doses of the Nal-Arg antagonist. Free alpha-subunit decreased 22 +/- 4%, 23 +/- 4%, and 28 +/- 3% at increasing doses of the Nal-Glu antagonist and 12 +/- 4%, 27 +/- 4%, and 30 +/- 7% with increasing doses of the Nal-Arg antagonist. For the Nal-Glu antagonist, suppression of LH was greater than that of FSH and free alpha-subunit at all doses (P less than 0.001), while FSH suppression was greater than that of free alpha-subunit at the highest dose only (P less than 0.05). For the Nal-Arg antagonist, LH suppression was greater than that of FSH or free alpha-subunit at all doses (P greater than 0.01), and FSH suppression exceeded that of free alpha-subunit at the 50 micrograms/kg dose. Suppression of LH was greater with the Nal-Glu antagonist than with the Nal-Arg antagonist at doses of 50 and 150 micrograms/kg (P less than 0.05), and FSH suppression was greater with the Nal-Glu antagonist at 150 micrograms/kg (P less than 0.01), while the degrees of maximum suppression were similar for the two different GnRH antagonists for free alpha-subunit.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1990

Immunoreactive inhibin alpha-subunit in human serum: implications for radioimmunoassay.

The specificity of the most widely used heterologous RIA for human serum inhibition was examined with regard to its cross-reactivity with the alpha-subunit of inhibin. Using a mixture of recombinant alpha inhibin proteins, including precursor and mature forms, the epitopic specificity of this antibody was localized entirely to the alpha-subunit. Furthermore, varying degrees of alpha inhibin immunoactivity were demonstrated in serum from normal subjects and patients with various reproductive disorders by both Western blot and RIA. These results demonstrate that data obtained using this RIA should be interpreted with caution as to the degree to which they reflect the presence of intact dimeric inhibin vs. alpha inhibin proteins in the circulation.

Antibodies↗
PubMed1990

Utility of free alpha-subunit as an alternative neuroendocrine marker of gonadotropin-releasing hormone (GnRH) stimulation of the gonadotroph in the human: evidence from normal and GnRH-deficient men.

To examine the hypothesis that the secretion of free alpha-subunit (FAS) can serve as an alternative to LH as a neuroendocrine marker of gonadotroph stimulation by GnRH in euthyroid humans, we have investigated the relationship of pulsatile FAS secretion in euthyroid GnRH-deficient men (n = 10) before and after exogenous GnRH stimulation and in normal men under the influence of endogenous GnRH secretion (n = 18). Before GnRH exposure, the GnRH-deficient men showed a complete absence of both LH and FAS pulses. During the initial 7 days of GnRH exposure, all GnRH-deficient men exhibited pulsatile release of FAS by the third day, whereas the appearance of pulsatile release of LH and FSH was more variable. Long term administration of GnRH led to pulses of LH and FAS that were 100% concordant with a demonstrable dose-response relationship between GnRH and FAS, which was quantitatively similar to but more exuberant than that for LH. All doses of GnRH that produced LH pulses within the normal adult range yielded supraphysiological FAS pulses. Analysis of distribution histograms of interpulse intervals and pulse amplitudes of LH and FAS in both normal and GnRH-deficient subjects demonstrated no significant difference between these glycoproteins in interpulse intervals in either the normal or GnRH-deficient groups or in the pulse amplitudes in the GnRH-deficient subjects. There was, however, a significant difference (P less than 0.01) between the distribution histogram of LH and FAS pulse amplitudes in normal men. We conclude that the pulsatile secretion of FAS in euthyroid men 1) is determined by GnRH secretion, 2) is the initial glycoprotein to be secreted in a pulsatile fashion from the gonadotroph during early GnRH exposure in GnRH-deficient men, 3) demonstrates a dose-response relationship to exogenous GnRH which is more robust than that of LH in GnRH-deficient men receiving GnRH, and 4) can, therefore, serve as a complementary and powerful tool with LH for the study of GnRH neurosecretory dynamics.

Adolescent↗
PubMed1990

Clinical review 15: Management of ovulatory disorders with pulsatile gonadotropin-releasing hormone.

Pulsatile GnRH therapy has yet to achieve widespread acceptance as an alternative to exogenous gonadotropin therapy in women with hypothalamic amenorrhea and complete GnRH deficiency. However, when a physiologically based replacement regimen of pulsatile GnRH is used, a high rate of ovulation and conception can be anticipated in patients with complete GnRH deficiency and hypothalamic amenorrhea. Women with polycystic ovarian syndrome may also benefit from pulsatile GnRH, although rates of ovulation are lower. Pretreatment with a GnRH agonist may improve these rates considerably, but experience is limited. Whether an iv or sc route of administration is chosen, a simplified clinical monitoring protocol can be created which requires a minimum of patient monitoring while assuring maximum safety. Seventy five nanograms per kg appears to be a reasonable initiating dose, with subsequent increases in those who do not respond. The frequency of GnRH administration is best based on the GnRH pulse frequency in normal women. However, further information is needed to determine whether such a variable frequency is clearly superior to a fixed frequency regimen. When used appropriately, pulsatile GnRH is safe, effective, and offers an excellent alternative to conventional gonadotropin therapy for women with disordered endogenous GnRH secretion. Most importantly, and as opposed to exogenous gonadotropin therapy, pulsatile GnRH can be administered by most physicians in the office setting without the necessity of on-line E2 monitoring. This feature will enable more patients to receive treatment by their local physicians, whereas exogenous gonadotropin therapy should be administered by appropriately equipped referral centers. In the future, further studies will be required to determine which other categories of patients might benefit from pulsatile GnRH.

Adult↗
PubMed1990

Divergent responses of gonadotropin subunit messenger RNAs to continuous versus pulsatile gonadotropin-releasing hormone in vitro.

Episodic GnRH input is necessary for the maintenance of LH and FSH secretion. In the current study we have assessed the requirement of a pulsatile GnRH signal for the regulation of gonadotropin alpha- and beta-subunit gene expression. Using a dispersed rat pituitary perifusion system, GnRH (10 nM) was administered as a continuous infusion vs. hourly pulses. Secretion of free alpha-subunit, LH, and FSH were monitored over 5-min intervals for the entire 12-h treatment period before the responses of alpha, LH beta, and FSH beta mRNAs were assessed. Basal release of all three glycoproteins declined slowly over 6-8 h before reaching a plateau. The cells were responsive to each pulse of GnRH, but continuous GnRH elicited only a brief episode of free alpha-subunit, LH, and FSH release, followed by a return to unstimulated levels. Despite the similar patterns of secretion, differences were observed in the responses of gonadotropin mRNAs to the two modes of GnRH. alpha mRNA increased in response to continuous (1.6-fold) or pulsatile (1.7-fold) GnRH. FSH beta mRNA was suppressed to 48% of the control value after continuous GnRH, but was stimulated over 4-fold by the pulses. LH beta mRNA was unresponsive to either treatment paradigm. We conclude that in vitro 1) alpha mRNA levels are increased in response to GnRH independent of the mode of stimulation; 2) under the conditions studied, LH beta mRNA levels are unresponsive to either mode of GnRH input; and 3) the response of FSH beta mRNA to GnRH is highly dependent on the mode of administration, with levels depressed in response to continuous GnRH, but stimulated by pulsatile GnRH.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Validation of highly specific and sensitive radioimmunoassays for lutropin, follitropin, and free alpha subunit in unextracted urine.

Measurement of the urinary excretion of lutropin (LH) and follitropin (FSH) and their common free alpha subunit (FAS) assists in monitoring the maturation of the hypothalamic-pituitary-gonadal axis and in understanding the physiology of the pituitary glycoprotein hormones. Here we describe sensitive, specific polyclonal radioimmunoassays for LH and FSH and a monoclonal radioimmunoassay for FAS for use with urine--assays unperturbed by alterations in urinary pH or osmolarity within the broad physiological range encountered in urine. Concordance between LH, FSH, and FAS concentrations in extracted and unextracted urine samples was high. Linearity and parallelism with the standard curves was observed with addition of 25 to 200 microL of unextracted urine. No effect on glycoprotein concentration was seen after as many as 10 freeze-thaw cycles. The need for extraction was further obviated by the high sensitivity of each assay, reflected by minimum detectable doses well below the concentrations encountered in patients' samples. Thus we have measured gonadotropins in unextracted urine as precisely as in extracted urine. We also have demonstrated an equally versatile assay for urinary alpha subunit, using a monoclonal antibody of high specificity for this monomer in its free, uncombined form. These radioimmunoassays complement assays of gonadotropins and free alpha subunit in serum and will allow longitudinal investigations otherwise limited by the constraints of the patient's blood volume.

Adult↗
PubMed1989

Interpulse interval of GnRH stimulation independently modulates LH secretion.

To examine the importance of the interpulse interval of gonadotropin-releasing hormone (GnRH) stimulation in modulating gonadotroph responsiveness, a fixed individualized dose of GnRH was administered to eight GnRH-deficient men at intervals selected randomly from the distribution of luteinizing hormone (LH) interpulse intervals of normal men. The responses were compared with data derived from a study of LH pulses in 20 normal men. A positive relationship was found between LH pulse amplitude and the preceding interpulse interval both in the GnRH-deficient (P less than 0.05) and in the normal (P less than 0.003) men. The distributions of LH pulse amplitudes appeared to differ between the two groups with failure of the study paradigm to reproduce the distribution of low-amplitude pulses of the normal men in the GnRH-deficient men. There was significantly more variability about the line that related interpulse interval and LH amplitude in the normal men (P less than 0.004) in whom the amount of GnRH could vary physiologically. This difference remained significant both for pulses with amplitudes below (P less than 0.01) or above (P less than 0.03) the mean of the normal men. These studies demonstrate that the GnRH interpulse interval is an independent determinant of pituitary responsiveness and that alterations in the amount of GnRH secreted from the hypothalamus are an important determinant of LH pulse amplitude in men.

Adult↗