Pituitary Responsiveness to Synthetic Luteinizing Hormone Releasing Hormone (LH‐RH) During the Menstrual Cycle and in Female Hypogonadism (original) (raw)
Related papers
European journal of endocrinology, 1979
In normal females, the injection of 25 \g=m\g of LH-RH (acute test) induced a greater LH and FSH release from the pituitary in the mid-luteal than in the mid-follicular phase of the menstrual cycle. In normal males, the responsiveness to 25 \g=m\g LH-RH was greater than that in females at mi d\x=req-\ follicular but not at the luteal stage. The pituitary response to the prolonged LH-RH infusion (0.21 \g=m\g/min/8h) was similar in both phases of the cycle of the females with a decline in serum gonadotrophins after the 4th hour and was paralleled by a significant increase of plasma oestradiol levels. In males the LH, but not the FSH secretion was lower as compared to female subjects, and gonadotrophin levels did not show a fall during the infusion. The acute injection of 25 \g=m\g LH-RH at the end of a prolonged infusion induced the same response in the female subjects in both phases of the cycle. In males, the acute test following prolonged infusion produced a similar LH secretion, but a lower FSH response than in females. The comparison of the acute test alone and that preceded by a prolonged LH-RH infusion, demonstrated that, in females, the only significant differences consisted of a greater LH secretion in the former test in the mid-luteal phase. In males there was greater FSH secretion in the acute isolated test than when this test was given after the prolonged infusion.
Journal of Endocrinology, 1974
SUMMARY The role of ovarian hormones in the development of increased sensitivity of the anterior pituitary gland to synthetic luteinizing hormone releasing factor (LH-RF) which occurs before and during the preovulatory surge of luteinizing hormone (LH) in the rat has been examined. The response of the pituitary gland was determined, with respect to the secretion of LH and follicle-stimulating hormone (FSH), after the intravenous injection of 50 ng LH-RF/100 g body weight. The LH-RF was injected 30–60 min after the administration of sodium pentobarbitone at either 13.30 h or 18.80 h of pro-oestrus. Blood samples were collected immediately before and at frequent intervals after the injection of LH-RF, and the concentration of LH and FSH in these samples was measured by radioimmunoassay. Ovariectomy at 10.00–11.00 h of dioestrus reduced the LH response to LH-RF injected at 14.00 h of pro-oestrus, while oestradiol benzoate administered immediately after ovariectomy restored and even aug...
Clinical Endocrinology, 1987
LH pulse secretion changes during the menstrual cycle from a rapid regular pattern in the follicular phase to a slower and irregular pattern in the luteal phase. To determine whether the irregular LH pulse pattern in the luteal phase reflects altered GnRH secretion or altered pituitary responsiveness to GnRH, we gave low dose GnRH pulses (25 ng/kg i.v.) every 2 h or every hour for 10 or 12 d to three women with isolated GnRH deficiency. After 4 d of GnRH alone, oestradiol (E2) was given and after 6 d progesterone (P) was added to mimic the hormonal milieu of the luteal phase. LH and FSH were measured every 4 h throughout and also every 20 min for 6 or 12 h, before and after GnRH alone (day 0 and day 4), after E2 (day 6), and after E2+P (day 10 and day 12). Both GnRH pulse frequencies resulted in a rapid increase in plasma FSH to peaks on day 4 (every 2 h) and day 2 and 3 (every hour). FSH concentrations then declined as plasma E2 rose to 50-80 pg/ml reflecting the selective inhibitory effect of E2 on FSH release. Plasma LH was also increased after the hourly GnRH injections and this regimen was associated with a more rapid rise in E2 reflecting follicular maturation. In contrast to the differences in mean hormone concentrations, administration of GnRH at both frequencies resulted in sustained one-on-one responsiveness of LH that was maintained in the presence of both oestrogen and progesterone at mid-luteal phase concentrations. We conclude that the slow frequency of LH pulses observed during the luteal phase reflects decreased GnRH pulse frequency rather than impaired pituitary responsiveness to GnRH.
The Journal of Clinical Endocrinology & Metabolism, 1999
During the follicular phase of the menstrual cycle, FSH stimulates follicular growth, granulosa cell aromatase activity, induction of LH receptors on the granulosa cell membrane, and estradiol secretion. As a result of negative feedback of estradiol on the pituitary, serum FSH concentrations decline. Despite the fall in FSH concentrations, the maturing follicle continues to develop to the preovulatory stage. In a prospective randomized trial, we tested the hypothesis that a key mechanism by which the dominant follicle continues to develop in the face of decreasing concentration of FSH is by acquiring LH responsiveness. In 24 women, pituitary gonadotropin secretion was downregulated with a GnRH agonist. Follicular growth was then stimulated with recombinant human FSH (r-hFSH) until a 14-mm follicle was identified by ultrasound. The women were then randomized to 1 of 4 groups for a 2-day period: continued r-hFSH treatment, substitution of r-hFSH with saline, low dose r-hLH (150 IU, twice daily), or high dose r-hLH (375 IU, twice daily). Serum estradiol concentrations in the women receiving saline declined by the end of the 2-day randomization period. In contrast, serum estradiol concentrations continued to rise in women receiving either r-hFSH or r-hLH compared with those in the saline-treated group (P Ͻ 0.05). Pregnancies occurred in each of the gonadotropin treatment groups. These findings indicate that once FSH initiates follicular growth, either FSH or LH is capable of sustaining follicular estradiol production. Extrapolating these findings to the normal menstrual cycle suggests that the maturing follicle may continue to develop in the presence of diminishing FSH concentrations by acquiring the capacity to respond to LH.
Studies in reproductive endocrinology
2014
A group of six hypogonadal males with low serum levels of FSH and LH, and otherwise normal pituitary function, underwent tests in which 100-300 ug of LHRH [Lutein izing Hormone Releasing Hormone] was injected rapidly intravenously. All four possible combinations of serum LH and FSH responses were observed. That is, failure of FSH and LH to rise; an increase in both FSH and LH; and an increase in FSH only, or in LH only. The heterogeneity of the LH and FSH responses to LHRH indicates the complexity of the etiology of this group of disorders, whose clinical expression is hypogonadotropic hypo gonadism .
Endocrinology, 1996
The LH secretory response of gonadotropes to GnRH varies during the estrous cycle of the rat. The increased secretion of estrogens during the 24-48 h before the preovulatory surge of LH secretion and the enhanced quantities of progesterone secreted acutely during the surge elevate the responsiveness of hypophysial gonadotropes to GnRH. However, the cause of the massive decline in GnRH responsiveness that occurs during or after the surge remains unknown. In the present studies, we investigated the possibility that it is due to GnRH-induced desensitization of gonadotropes. Dispersed pituitary cells from proestrous and estrous rats were preincubated with GnRH (3 or 6 h, 10ml' or lo-' M), progesterone (13 h, 100 or 200 nM), GnRH plus progesterone, or medium alone. Then, the cells were retrypsinized to permit performance of the reverse hemolytic plaque assay for measurement of LH secretion, during which they were
Journal of Endocrinology, 1976
Blood was collected from the cut pituitary stalk of male and female rats before and during the application of an electrical stimulus to the medial preoptic area. The plasma was assayed for immunoreactive LH releasing factor (RF) by a double antibody radioimmunoassay using a specific antiserum raised in rabbits against the free acid derivative of the decapeptide LH-RF conjugated to bovine serum albumin. The decapeptide (used as a standard) and pituitary stalk plasma cross-reacted in a similar manner with the antiserum. Stimulation of the preoptic area increased significantly the amount of LH-RF in pituitary stalk plasma in both male and female rats. The increase in LH-RF was linearly related to the strength of the stimulating current, and the amount of LH-RF liberated diminished on cessation of the stimulus. The concentration of LH-RF in pituitary stalk plasma from female rats was significantly greater than that in jugular venous plasma. The magnitudes of the mean increments of LH-RF in pituitary stalk plasma (stimulation minus pre-stimulation values) at various times of the oestrous cycle in female rats suggests that between 18.00 h of dioestrus and 13.00 h of pro-oestrus there is an increase in sensitivity of the LH-RF secretory mechanism to electrical stimulation. However, the increments decreased in magnitude between 13.00 and 18.00 h of pro-oestrus, indicating that the marked increase in responsiveness of the hypothalamo-hypophysial system to electrical stimulation which occurs during this period is due mainly to a change in sensitivity of the pituitary gonadotrophs to LH-RF. The LH-RF in pituitary stalk plasma collected before application of the stimulus was higher at some of the times examined during pro-oestrus than at other times of the oestrous cycle. A higher level of the secretion of the factor may be important for the full development of the priming effect of LH-RF and, consequently, the marked increase in responsiveness of the pituitary gland which occurs during the afternoon of pro-oestrus.
Reproductive Biology and Endocrinology, 2014
Background: Luteinizing hormone (LH) activity in human menopausal gonadotropin (hMG) preparations is derived from human chorionic gonadotropin (hCG) rather than LH. Therefore, we aimed to determine whether there are similarities in the endocrine and follicular profiles of serum and follicular fluid from controlled ovarian stimulation with the recombinant gonadotropins follicle-stimulating hormone plus luteinizing hormone (rFSH + rLH) or highly purified human menopausal gonadotropin (HP-hMG). Methods: We performed a prospective observational study with 50 oocyte donors that received either a combination of recombinant gonadotropins (rFSH + rLH) or a mixture of urinary gonadotropins (HP-hMG) plus purified urinary FSH (uFSH). Results were analyzed using Student's t-test to compare continuous variables and the chi-squared test to compare proportions. P-values < 0.05 were considered statistically significant.
Clinical Endocrinology, 1976
The effect of clomiphene (100 mg daily for 10 days) and ethinyl oestradioI (100 pg daily for 10 days) on the gonadotrophin response to synthetic LHRH has been investigated in two groups of five normal males. A third group of five men served as control group. LHRH, 25 pg, was injected intravenously on days 0,4, 7 and 10 and the response of serum LH and FSH was monitored by radioimmunoassay. In contrast to the wide inter-individual variation of the response pattern, the intraindividual variation of the response to LHRH in the control group was small. Clomiphene induced a significant elevation of the baseline levels of LH and FSH after a few days of treatment; the pituitary responsiveness to LHRH, however, was significantly reduced. Oestrogen treatment resulted in a uniform suppression of both basal gonadotrophin levels and pituitary responsiveness. The decreased gonadotrophin response to LHRH during clomiphene treatment is thought to be caused by a relative and temporary pituitary depletion of the releasable gonadotrophin content. Although the suppression of LH and FSH response during oestrogen treatment may point to a direct inhibitory effect of oestrogen on pituitary gonadotrophin release, an indirect hypothalamic pathway, through suppression of endogenous LHRH, cannot be ruled out.