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Biomedical subjects

W F Crowley

Publications and source records attributed to W F Crowley.

At least 127 records · Page 7Linked to original sources
PubMed1989

Gonadotropin and alpha-subunit responses to chronic gonadotropin-releasing hormone analog administration in patients with glycoprotein hormone-secreting pituitary tumors.

Pituitary tumors secreting intact glycoprotein hormones (LH, FSH, and TSH) and/or alpha-subunit are being increasingly recognized. Because chronic administration of GnRH analogs decreases gonadotropin secretion in normal subjects, we investigated gonadotropin and alpha-subunit responses to chronic GnRH analog administration in five men with glycoprotein hormone-secreting pituitary tumors. Two patients (patients A and B) received the GnRH agonist analog (D-Trp6-Pro9-NEt-LHRH) for 4 weeks as a daily sc dose (8 micrograms/kg.day). In both, secretion of LH and/or alpha-subunit increased markedly. Subsequently, three patients received a higher analog dose (32 micrograms/kg.day) for a longer duration (8 weeks). One patient with a LH- and FSH-secreting tumor (patient C) had a highly significant (P less than 0.001) fall in serum LH and FSH concentrations; however, alpha-subunit secretion increased. During a subsequent study, when this patient received a lower dose (8 micrograms/kg.day) for 8 weeks, gonadotropin suppression also occurred. In two additional patients who received this dose (32 micrograms/kg.day), it had a persistent agonist effect on FSH beta (patient D) and alpha-subunit secretion (patient E). A marked increase in alpha-subunit secretion occurred in all five patients, regardless of whether basal serum alpha-subunit concentrations were elevated. These patients received the GnRH analog at doses 2-8 times greater than those that suppress gonadotropin secretion in normal men. Serum LH and FSH concentrations decreased in only one patient with a gonadotropin-secreting adenoma. The serum LH and FSH responses to acute GnRH stimulation did not predict the gonadotropin responses to chronic GnRH analog administration. Thus, gonadotropin and alpha-subunit production by most pituitary adenomas is augmented during chronic GnRH analog administration, consistent with defective GnRH desensitization in the adenomatous tissue. Despite the heterogeneous gonadotropin responses to the GnRH analog in these patients, serum alpha-subunit levels increased in all patients, indicating dissociation in the secretion of intact gonadotropins and alpha-subunit.

Adenoma↗
PubMed1989

Normal structure of the gonadotropin-releasing hormone (GnRH) gene in patients with GnRH deficiency and idiopathic hypogonadotropic hypogonadism.

Idiopathic hypogonadotropic hypogonadism (IHH) is a genetic disorder in which a lack of hypothalamic GnRH secretion forms the basis for impaired gonadotropin release. Several lines of evidence, including an animal model of GnRH deficiency, suggest that an abnormality at the level of the GnRH gene might be responsible for the secretory defect in patients with IHH. We examined 13 patients (11 males and 2 females) with IHH documented by standard clinical and biochemical criteria, including apulsatile basal LH secretion which was reversed by administration of pulsatile GnRH. The structure of the GnRH gene in these patients was determined using Southern blot analyses. In every case EcoRI digestion revealed a 10-kilobase fragment including the entire GnRH gene, eliminating deletion of the gene as a cause of IHH. Multiple restriction enzymes (Xba I, BglII, BamHI, PstI, TaqI, RsaI, EcoRV, and BglI) and hybridization probes to exons 2 and 4 of the gene were used to search for polymorphisms or relatively small deletions or rearrangements in the GnRH gene. Polymorphisms were not identified, and deletions or rearrangements involving more than 200 basepairs were excluded. We conclude that a major rearrangement of the GnRH gene is not a common basis for IHH in humans.

Adolescent↗
PubMed1989

Pulsatile gonadotropin secretion after discontinuation of long term gonadotropin-releasing hormone (GnRH) administration in a subset of GnRH-deficient men.

Normal pituitary and gonadal function can be maintained with long term pulsatile GnRH administration in men with idiopathic hypogonadotropic hypogonadism (IHH), and both pituitary and gonadal priming occur during the process of GnRH-induced sexual maturation. Still, the long term effects of discontinuing GnRH therapy in IHH men have not been examined. Therefore, we evaluated the patterns of gonadotropin and alpha-subunit secretion before and after a prolonged period of pulsatile GnRH administration in 10 IHH men. Before exogenous GnRH stimulation, no patient had any detectable LH pulsations. In 6 of these men, who were typical of most of our IHH patients (group I), no LH pulsations were detectable after cessation of GnRH administration. However, in the other 4 men (group II), LH pulsations were easily detectable despite cessation of exogenous GnRH stimulation, and the amplitude (9.3 +/- 3.5 IU/L) and frequency (13.8 +/- 1.7 pulses/day) of these LH pulses were similar to those in 20 normal men (10.6 +/- 0.7 IU/L and 11.0 +/- 0.7 pulses/day). Three of these 4 men in group II maintained normal serum testosterone levels after discontinuation of GnRH delivery. To determine if there were any characteristics that might be useful in predicting which IHH men could maintain normal pituitary-gonadal function after long term GnRH administration, we evaluated various clinical and hormonal parameters at the time of initial presentation. Mean alpha-subunit levels (P less than 0.01) and alpha-subunit pulse amplitude (P less than 0.02) were significantly higher in the group II than the group I men, suggesting that the group II patients had partial, rather than complete, deficiency of endogenous GnRH secretion. None of the other parameters that were assessed distinguished the two groups. We conclude that gonadotropin and sex steroid levels return to their pretreatment state in the majority of IHH men when long term GnRH administration is discontinued. Normal pituitary-gonadal function can be maintained after discontinuation of long term GnRH administration in a rare subset of IHH men who present with higher levels of alpha-subunit. We hypothesize that these latter IHH men have an incomplete GnRH deficiency and that long term exogenous GnRH administration induces pituitary and gonadal priming, which subsequently enables them to sustain normal pituitary and gonadal function in response to their own enfeebled GnRH secretion.

Adult↗
PubMed1989

Increases in bone density during treatment of men with idiopathic hypogonadotropic hypogonadism.

To assess the effects of gonadal steroid replacement on bone density in men with osteoporosis due to severe hypogonadism, we measured cortical bone density in the distal radius by 125I photon absorptiometry and trabecular bone density in the lumbar spine by quantitative computed tomography in 21 men with isolated GnRH deficiency while serum testosterone levels were maintained in the normal adult male range for 12-31 months (mean +/- SE, 23.7 +/- 1.1). In men who initially had fused epiphyses (n = 15), cortical bone density increased from 0.71 +/- 0.02 to 0.74 +/- 0.01 g/cm2 (P less than 0.01), while trabecular bone density did not change (116 +/- 9 compared with 119 +/- 7 mg/cm3). In men who initially had open epiphyses (n = 6), cortical bone density increased from 0.62 +/- 0.01 to 0.70 +/- 0.03 g/cm2 (P less than 0.01), while trabecular bone density increased from 96 +/- 13 to 109 +/- 12 mg/cm3 (P less than 0.01). Cortical bone density increased 0.03 +/- 0.01 g/cm2 in men with fused epiphyses and 0.08 +/- 0.02 g/cm2 in men with open epiphyses (P less than 0.05). Despite these increases, neither cortical nor trabecular bone density returned to normal levels. Histomorphometric analyses of iliac crest bone biopsies demonstrated that most of the men had low turnover osteoporosis, although some men had normal to high turnover osteoporosis. We conclude that bone density increases during gonadal steroid replacement of GnRH-deficient men, particularly in men who are skeletally immature.

Adult↗
PubMed1989

Closed intravenous administration of gonadotropin-releasing hormone: safety of extended peripheral intravenous catheterization.

The use of pulsatile gonadotropin-releasing hormone is an effective means of inducing ovulation, but requires prolonged intravenous (IV) or subcutaneous administration. We hypothesized that the use of self-contained infusion pumps using fluids maintained in a closed system would permit safe peripheral IV administration of gonadotropin-releasing hormone, and possibly other hormones, over prolonged intervals. Thirty-eight female patients undergoing pulsatile IV gonadotropin-releasing hormone therapy were followed for 1958 catheter days (230 catheters). Catheters were removed for signs of local inflammation, at the completion of a treatment episode or, initially, at routine intervals of 7-10 days. There were no episodes of fever (temperature over 37.5C) and three episodes of local inflammation. The incidence of significant catheter-tip cultures was 11%, and none were associated with local inflammation. There were four positive blood cultures (2%), none associated with local or systemic signs of infection. We conclude that the use of a closed system of prolonged peripheral IV cannulation is relatively safe when combined with fastidious care of the catheter site and careful outpatient monitoring for long-term administration of pulsatile gonadotropin-releasing hormone.

Adult↗
PubMed1988

Pituitary and gonadal responsiveness is enhanced during GnRH-induced puberty.

We hypothesized that the hypothalamic gonadotropin-releasing hormone (GnRH) signal that initiates sexual maturation is further amplified at both the pituitary and gonadal levels during puberty. To test this theory, six GnRH-deficient men were monitored during administration of exogenous GnRH at a physiological frequency for greater than or equal to 9 mo. GnRH doses were progressively increased until normal testosterone (T) concentrations and secondary sexual development were achieved. This "optimized" dose of GnRH was then sustained for at least 6 mo to allow maturation of the hypothalamic-pituitary-gonadal axis. The GnRH dose was then progressively decreased to a level that had been unable to stimulate normal T secretion before sexual maturation. Changes in pituitary responsiveness were analyzed in four of the six men by comparing gonadotropin responses to identical doses of GnRH before and after sexual maturation. Mean serum luteinizing hormone and follicle-stimulating hormone levels as well as luteinizing hormone pulse amplitudes were greater after the induction of sexual maturation than before despite identical doses of GnRH. Both pituitary and gonadal responsiveness was then analyzed in the remaining two subjects by choosing periods of evaluation where endogenous gonadotropin levels were matched before and after the period of sexual maturation. Serum T concentrations were greater after sexual maturation than before despite equivalent gonadotropin input to the testes and LH pulse amplitudes. Thus the testicular responsiveness to gonadotropins increased during sexual maturation. After initiation of puberty by GnRH secretion, amplification at both the pituitary and gonadal levels contributes to sexual maturation in the human.

Adult↗
PubMed1988

Neuroendocrine-gonadal axis in men: frequent sampling of LH, FSH, and testosterone.

Previous studies of episodic hormone secretion of the hypothalamic-pituitary-gonadal axis in normal men have produced conflicting results due to examinations of small cohorts of subjects or to limited sampling techniques. We evaluated gonadotropin and testosterone (T) secretory patterns in 20 normal men by sampling blood at 10-min intervals for luteinizing hormone (LH) and follicle-stimulating hormone (FSH). T concentrations were also analyzed at 20-min intervals in 10 subjects. A previously unappreciated spectrum of gonadotropin and T secretory patterns was observed in normal men. Both mean LH concentrations and mean LH pulse amplitudes varied fourfold between individuals. LH interpulse intervals varied from 30 to 480 min (mean 119 +/- 32). Results also suggested a relative refractory period at the level of the hypothalamus or pituitary. In three subjects, a striking nighttime accentuation of LH pulsations was noted. Through use of Fourier analysis, a diurnal variation in LH was observed in the population (P less than 0.02). Mean FSH levels showed marked variation between individual subjects, with discrete pulses rarely observed. No diurnal variation in FSH secretion was noted. Serum T concentrations determined at 6-h intervals ranged from 105 to 1,316 ng/dl between subjects. When T was measured at 20-min intervals, marked intermittent declines in the T concentrations to levels well below the normal range were observed in 3 of 10 subjects. T secretion was found to lag behind LH secretion by approximately 40 min (P less than 0.02).

Adult↗
PubMed1988

Impact of sex steroids and their suppression on skeletal growth and maturation.

Forty girls with central precocious puberty (CPP) were studied before and during 1-3 yr of luteinizing hormone-releasing factor (LHRH) agonist (LHRHa) administration to examine the impact of gonadal steroid secretion and its suppression on skeletal growth and maturation. Pubertal growth velocity (GV) was 10.1 +/- 0.7 (SE) cm/yr and, when normalized for chronological age (CA) and bone age (BA), demonstrated that the effects of sex steroids were most profound in patients with the youngest CA and BA. GV decreased significantly to 5.8 +/- 0.3 (n = 40), 4.6 +/- 0.3 (n = 30), and 3.2 +/- 0.6 cm/yr (n = 12) during 3 yr of gonadal suppression and correlated negatively with starting BA. Skeletal maturation was markedly accelerated by premature sex steroid secretion (BA/CA = 1.8 +/- 0.1), was slowed significantly with gonadal suppression (mean delta BA/delta CA less than 1), and also was negatively correlated with the starting BA. Cumulative increases in predicted adult height were observed regardless of starting BA and averaged +2.0 +/- 0.4, +5.2 +/- 0.5, and +6.7 +/- 1.2 cm after 1, 2, and 3 yr of gonadal suppression. The comparable changes in height predictions across all BAs despite highly variable GVs underscore the need for use of developmental (i.e., BA-based) rather than CA-based standards in the analysis of growth during gonadal steroid exposure and suppression in childhood.

Body Height↗
PubMed1988

Alterations of the hypothalamic GnRH interpulse interval sequence over the normal menstrual cycle.

Luteinizing hormone (LH) is released in a pulsatile fashion from the anterior pituitary in response to hypothalamic gonadotropin-releasing hormone (GnRH) secretion. Previous autocorrelation analysis of the sequence of interpulse intervals of LH secretion in normal men has supported the hypothesis that the underlying hypothalamic mechanism of GnRH secretion governing episodic LH release is a renewal process, indicating that hypothalamic "memory," if present, does not extend back further in time than the preceding secretory pulse. A similar analysis of pulsatile LH secretion was undertaken in 45 studies of normal women, obtained throughout the menstrual cycle. Analysis of these studies revealed a process consistent with renewal throughout the follicular and early luteal phases. However, this relationship appears to break down in the mid-to-late luteal phase, indicating that alternative feedback pathways provide an overriding influence on the underlying renewal process of hypothalamic GnRH secretion. Pulsatile progesterone secretion by the corpus luteum, which first emerges at this stage of the menstrual cycle, may be the agent responsible for this feedback.

Female↗
PubMed1988

Effects of decreasing the frequency of gonadotropin-releasing hormone stimulation on gonadotropin secretion in gonadotropin-releasing hormone-deficient men and perifused rat pituitary cells.

The effects of decreasing the frequency of pulsatile gonadotropin-releasing hormone (GnRH) stimulation on pituitary responsiveness were studied in (a) men with isolated GnRH deficiency who had achieved normal sex steroid levels during prior long-term pulsatile GnRH replacement and (b) perifused dispersed pituitary cells from male rats in the absence of sex steroids. In three groups of four GnRH-deficient men, the frequency of GnRH stimulation was decreased at weekly intervals from (a) every 2-3-4 h (group I), (b) every 2-8 h without testosterone replacement (group II), or (c) every 2-8 h with testosterone replacement (group III). In three groups of three columns of perifused dispersed pituitary cells, pulses of GnRH were administered every 2, 4, or 8 h. In groups I and II, mean area under the luteinizing hormone (LH) curve increased (P less than 0.025) and serum testosterone levels fell (P less than 0.035) as the frequency of GnRH stimulation was decreased. In group III, the area under the LH curve also increased (P less than 0.01) although serum testosterone levels were constant, thereby demonstrating that the increase in pituitary responsiveness to slow frequencies of GnRH stimulation occurs independently of changes in the sex steroid hormonal milieu. The area under the LH curve also increased in the perifused dispersed rat pituitary cells when the frequency of GnRH administration was decreased to every 8 h (P less than 0.05), thus demonstrating that the enhanced pituitary responsiveness to slow frequencies of GnRH stimulation is maintained even in the complete absence of gonadal steroids. Nadir LH levels fell in all three groups (P less than 0.01) as the frequency of GnRH stimulation was decreased. In contrast, mean peak LH levels, the rate of LH rise, and the rate of endogenous LH decay were constant as the frequency of GnRH stimulation was decreased. Finally, as the GnRH interpulse interval increased, mean LH levels fell, and mean follicle-stimulating hormone levels were stable or fell. These results indicate that (a) pituitary responsiveness to GnRH increases at slower frequencies of GnRH stimulation in models both in vivo and in vitro, (b) these changes in pituitary responsiveness occur independently of changes in gonadal steroid secretion, and (c) the increases in LH pulse amplitude and area under the curve at slow frequencies of GnRH stimulation are due to decreases in nadir, but not peak, LH levels. Slowing of the frequency of GnRH secretion may be an important independent variable in the control of pituitary gonadotropin secretion.

Adult↗
PubMed1988

Epitope mapping of human luteinizing hormone using monoclonal antibodies.

To establish structure-function relationships for human (h) LH, 14 murine monoclonal antibodies (MABs) to hLH were characterized in terms of their affinity of binding (Ka), their specificity for intact glycoproteins and their subunits, their paratopic relationships, and their ability to interfere with the biological activity of hLH. The Ka values obtained ranged between 2.4 x 10(6) and 1.0 x 10(10) for intact hLH and between 2.3 x 10(6) and 7.5 x 10(8) liters/M for the free alpha- and beta-subunits, indicating that, in general, the antibodies showed higher avidity for the intact hormone. Six MAB recognized both the intact and free alpha-subunit of hLH, cross-reacted with intact hCG, hFSH, and hTSH, and thus appeared to be alpha-directed. Four MAB were beta-directed, recognizing both intact hLH and its free beta-subunit. One of these beta-directed MABs also cross-reacted with intact hCG, hFSH, and hTSH, while two others recognized both intact and free beta-subunits of hLH and hCG. The fourth beta-directed MAB was quite specific for intact hLH and its beta-subunit. The remaining four MABs recognized epitopes only on the intact hormone; three recognized intact hLH and hCG, and the fourth was specific for intact hLH. Their paratopic relationships tested in competitive binding studies resulted in either mutual competition or complementarity, sometimes with cooperativity. Biointerference, defined as the ability to inhibit hLH-induced testosterone biosynthesis in dispersed rat Leydig cells, indicated that three of the alpha- and one of the beta-directed antibodies neutralized the biological response of hLH in this bioassay in a dose-responsive manner. Their ability to inhibit hLH bioactivity largely paralleled their affinity constants. Our data have allowed us to establish a tentative topographic relationship of epitopes to the biological region of the molecule of hLH, foreshadowing (in additive binding studies) some of the possible combinations of antibodies that might allow us to design two- or multiple-site immunometric assays in which measurement of immunoactive LH reflects biological activity. In addition, these studies suggest that both the alpha- and beta-subunits participate in LH receptor binding and/or biological activity.

Animals↗
PubMed1988

Hyperfunction of the hypothalamic-pituitary axis in women with polycystic ovarian disease: indirect evidence for partial gonadotroph desensitization.

To examine gonadotropin secretory frequency as a component of the disordered neuroendocrine regulation of gonadotropin secretion in women with polycystic ovarian disease (PCOD), we measured serum gonadotropin concentrations in 12 women with PCOD at 10-min intervals for periods of 12-24 h. The patterns of LH and FSH release in these patients were compared to the findings of 24 studies in 21 age-matched normal women during the early, mid- and late follicular phases (EFP, MFP and LFP) of their cycles. Serum sex steroid levels during the 12-24 h of study in the women with PCOD were compared to those in normal women studied during the follicular phase. The mean serum estradiol (E2) level in the women with PCOD was similar to that in normal women studied in the EFP, but lower than those in normal women in the MFP (P less than 0.05) and LFP (P less than 0.01). Mean serum estrone, however, was significantly higher in women with PCOD than in women in the EFP and MFP (P less than 0.05 and P less than 0.02, respectively), but lower than that in women in the LFP (P less than 0.02). Total and unbound testosterone (T) levels were significantly elevated in women with PCOD compared to those in normal women at all stages of the follicular phase (P less than 0.001). The mean serum LH concentration and LH pulse amplitude were markedly elevated in the women with PCOD compared to normal women at all three stages of the follicular phase (P less than 0.05 or less). In addition, LH pulse frequency was faster in women with PCOD [24.8 +/- 0.9 ( +/- SE) pulses/24 h] than that in women in the EFP (15.6 +/- 0.7; P less than 0.01), MFP (22.2 +/- 1.1; P less than 0.05) and LFP (20.8 +/- 1.2; P less than 0.01). This increased LH pulse frequency in women with PCOD correlated with ambient serum E2 levels on the day of study (r = 0.84; P less than 0.001), but not with serum estrone, T, or unbound T. Repeat studies in four women with PCOD demonstrated a similarly abnormal gonadotropin secretory pattern in each. We conclude that 1) women with PCOD have an increase in both the amplitude and frequency of LH secretion compared to those in normally cycling women throughout the follicular phase; 2) the defect in women with PCOD is reproducible.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1988

Changes in growth and serum growth hormone and plasma somatomedin-C levels during suppression of gonadal sex steroid secretion in girls with central precocious puberty.

Suppression of gonadal sex steroid secretion in children with central precocious puberty (CPP) by LHRH analogs affords an opportunity to study sex steroid modulation of GH and somatomedin-C (Sm-C) secretion and to examine the role of GH and Sm-C in pubertal and prepubertal statural growth. Nocturnal serum GH and plasma Sm-C levels were measured in 10 preadrenarchal girls [mean age, 3.0 +/- 0.6] ( +/- SEM) yr with CPP before and during 2 yr of LHRH analog-induced gonadal suppression. Their mean height velocity, initially 4.6 +/- 0.6 ( +/- SEM) SD above the mean for chronological age, decreased to -0.1 +/- 0.4 SD during 12-24 months of ovarian suppression (P less than 0.00005). The mean peak nocturnal plasma GH level was 22.5 +/- 5.4 ( +/- SEM) micrograms/L during puberty, and it decreased to 10.2 +/- 2.1 micrograms/L after 3 months of suppression of gonadarche. This decrease persisted throughout the 2 yr of gonadal suppression (P less than 0.05). The reduction in GH secretion was accompanied by a decrease in mean plasma Sm-C levels from 3.5 +/- 0.7 to 1.5 +/- 0.2 U/mL after 3 months of suppression of gonadal sex steroids, which persisted during 2 yr of gonadal suppression (P less than 0.01). Suppression of ovarian function in girls with CPP results in decreased height velocity. This slowing of growth occurs in association with decreased nocturnal serum GH and plasma Sm-C levels, suggesting that acceleration of growth during puberty is partially mediated by sex steroid-induced augmentation of GH secretion.

Age Determination by Skeleton↗
PubMed1988

Evidence of differential control of FSH and LH secretion by gonadotropin-releasing hormone (GnRH) from the use of a GnRH antagonist.

The differential regulation of immunoactive FSH and LH secretion by endogenous GnRH was studied using a GnRH antagonist, [Ac-D2Nal1,D4FPhe2,DTrp3,DArg6]GnRH (the NAL-ARG antagonist), in normal women in the early follicular phase of the menstrual cycle, and their responses were compared to those in two groups of control women. Pulsatile LH secretion was examined as an index of the completeness of blockade of endogenous GnRH secretion. There was a dose-dependent decrease in both the frequency and amplitude of LH pulses. At the highest dose, LH pulses were completely abolished within 20 min after sc administration of the GnRH antagonist and for a minimum of 8 h in all women. The mean plasma LH levels were reduced within the first 4 h after antagonist administration at all doses (P less than 0.001). The duration of LH suppression was influenced by antagonist dose, with a continued effect 24 h after administration of the 500 micrograms/kg dose only. The maximum degree of LH suppression was 40% after 50 micrograms/kg (n = 6), 60% after 150 micrograms/kg (n = 6), and 59% after 500 micrograms/kg (n = 5). In contrast, plasma immunoreactive FSH levels did not change after these doses of the NAL-ARG GnRH antagonist. The maximum degree of FSH suppression was 16%, and the changes in plasma FSH concentrations were not dose dependent. Serum antagonist concentrations rose within 30 min after its administration to mean peak levels of 7.5 +/- 2.1 (+/- SE), 20.4 +/- 6.1, and 151 +/- 21 ng/mL after the 50, 150, and 500 micrograms/kg doses, respectively. The half-time of the disappearance of the NAL-ARG GnRH antagonist from plasma was 8.8 +/- 1.5 h. While there were no effects of antagonist administration on hematological, hepatic, or renal function, three women developed urticaria distant from the site of injection when administered the highest dose. We conclude that blockade of GnRH receptors by a GnRH antagonist 1) effectively antagonizes the action of GnRH, as assessed by its ability to block pulsatile LH secretion and reduce mean plasma LH levels; and 2) inhibits LH release to a considerably greater degree than FSH release, providing further evidence of possible GnRH-independent FSH secretion.

Adult↗
PubMed1988

Improved measurement of free alpha subunit of glycoprotein hormones by assay with use of a monoclonal antibody.

Any exploration of the physiology of secretion of free alpha subunit of glycoprotein hormones in humans requires a sensitive assay system that shows low cross reactivity with the intact hormones (lutropin, follitropin, thyrotropin, and choriogonadotropin). We established and validated such an assay system with a monoclonal antibody for detection of free alpha subunit in serum with better sensitivity (detection limit, 30 ng/L) and less cross reactivity (0.67% with intact human lutropin) than with available polyclonal antibody methods. Thus, the specific epitope recognized by this antibody apparently is exposed only on the free or uncombined form of alpha subunit and is concealed after non-covalent combination with any beta subunit. Using Western blot analysis, we show that most of the cross reactivity is probably the result of contamination of the human lutropin standard (obtained from the National Hormone and Pituitary Program, NIH) with small amounts of free alpha subunit. With such a specific and sensitive method, it should be possible to obtain more-precise information regarding the secretion of free alpha subunit.

Antibodies, Monoclonal↗
PubMed1987

Sensitivity differences in reproductive/endocrine organs to chronically administered LHRH agonists in female rats.

The acute and chronic effects of two LHRH agonists on reproductive endocrine target organs were examined in female rats. Animals were injected twice daily with [(ImBzl)-D-His6,Pro9-NEt]LHRH (histrelin) or [D-Trp6,Pro9-NEt]LHRH for 1, 3, 5, 7, 11 or 28 days at 1, 10, 100 or 1000 micrograms/kg/day beginning in the luteal phase. The responses observed with the two agonists were similar. An initial stimulatory phase was observed on the first day of treatment with substantial increases in serum LH and progesterone levels. A significant diminution of hormone response was seen by day 3. Only 1000 micrograms/kg abolished the pituitary LH response at later treatment periods. Estrous cyclicity, ovarian and uterine weight, and progesterone and estradiol levels were inhibited in a time and dose dependent manner. The results demonstrate target organ sensitivity differences. In contrast to the relatively high doses needed to inhibit the pituitary response and decrease ovarian weight, doses as low as 1 microgram/kg were sufficient to decrease uterine weight. If these findings extrapolate to humans, it may be that conditions in which the desired therapeutic action is suppression of uterine tissue, may be treated with lower doses of LHRH agonists than conditions requiring complete gonadal suppression.

Adrenal Glands↗