Hypothalamo-hypophyseo-gonadal axis in individuals with chronic renal insufficiency subjected to hemodialysis

The role of pituitary and sexual hormones in 21 patients with chronic renal failure (CRF) and related impotence and loss of libido who were being treated by hemodialysis and in 15 normal male controls has been studied. In both groups the serum levels of FSH, LH and TSH, PRL before and after injection of both LHRH and TRH were measured as well as the basal levels of Testosterone (T) and Estradiol (E2). The results show similar values for testosterone in both groups and statistically significant higher basal values for FSH, LH, TSH and PRL and lower basal values for E2 in CRF patients.     

Effects of anticonvulsant monotherapy in pregnancy on the newborn endocrine system. Preliminary data

Pituitary-thyroid axis function and gonadotropin secretion were evaluated by a combined TRH and LHRH test in 4 newborn female infants appropriate for gestational age of mothers treated by AEDs throughout pregnancy. We found: high basal FSH levels with normal FSH reserve, normal LH-HCG levels both before and after LHRH stimulation, normal TSH and T4 levels both before and after TRH stimulation, high T3 basal values with a normal increase after TRH and low rT3 basal values. It is suggested an AED increased T4 deiodination towards T3 in the newborn liver without a marked impairment of the endocrine functions of the fetus.     

Effects of continuous LHRH infusion on plasma levels of LH and FSH in males, before and after oestrogen or anti-oestrogen treatment

In order to study the role of oestrogens on gonadotrophin release in the human male, LHRH was administered as an infusion at a constant rate of 0.5 micrograms/minute for 4 hours to 7 normogonadotrophic oligozoospermic men, 6 eugonadal male-to-female transsexuals and 9 eugonadal male volunteers. In agreement with in vitro data a biphasic release pattern of both LH and FSH was observed in eugonadal transsexuals as well as in normogonadotrophic oligozoospermic men. In the latter the release of LH was greater than in eugonadal transsexual males and volunteers, which points to a different functioning of the hypothalamic-pituitary unit in normogonadotrophic oligozoospermic men. On the other hand the FSH response to LHRH stimulation was normal in these men. Three months' treatment with the oestrogen-receptor antagonist tamoxifen (TAM) (10 mg twice daily) in the normogonadotrophic oligozoospermic men stimulated basal LH, FSH and testosterone (T) levels. The fact that gonadotrophin levels rose in spite of increased T levels, suggests a role of endogenous oestrogens in the negative feedback regulation of gonadotrophin release in these men. Upon TAM treatment the first phase, the plateau and the second phase of LH release were augmented, whereas only the plateau and the second phase of FSH release were increased. Six weeks' administration of the oestrogen ethinyloestradiol (EE) (10 micrograms three times a day) in the eugonadal transsexual males suppressed basal T and oestradiol (E2) levels without affecting basal gonadotrophin levels significantly. In EE-treated males the first phase of LH release tended to be lower, whereas the plateau of LH had decreased significantly. The second phase of LH was unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of ovariectomy at two periods of the year on LH and FSH basal concentrations and pituitary response to LHRH in the brown hare (Lepus europaeus)

In the brown hare, fertile mating takes place from the beginning of December to September. Seasonal variations of basal concentrations of LH and FSH, and pituitary response to a monthly i.v. injection of LHRH were studied in intact control females and in females ovariectomized during the seasonal anoestrus (OVX1) or during the breeding season (OVX2). In intact females, both basal and LHRH-stimulated LH levels showed an annual variation, with minimal values during anoestrus. During the breeding season, the LH response to LHRH exhibited a biphasic pattern. In contrast, there was no clear seasonal variation in basal and LHRH-stimulated FSH concentrations. After ovariectomy during anoestrus, basal LH remained low for 2 months and began to increase in December. After ovariectomy during the breeding season, LH basal concentrations increased within a few days after the operation. Thereafter, LH values remained high in both groups of females until September, and decreased significantly as in intact females. The pattern of LH release after LHRH remained monophasic in the two groups of ovariectomized females. In OVX1 females, the LH response increased as early as October, was maximum from December to April and decreased progressively until October. IN OVX2 females, the LH response decreased regularly after ovariectomy to a minimum in October. In the 2 groups of ovariectomized females, basal FSH concentrations and pituitary response to LHRH rose rapidly after ovariectomy and did not vary significantly thereafter. These results showed a direct central effect of season on the regulation of basal concentrations of LH, modulated by a negative feed-back of ovarian secretions during the breeding season. In intact hares, the enhanced LH response after LHRH during the breeding season was related to an acute positive effect of ovarian secretions. The regulation of FSH was less dependent on season and remained under a negative control of the ovary throughout the year.     

The hypothalamic-pituitary axis in diabetes mellitus

The hormonal response to LHRH and TRH was evaluated in three groups of male diaetics. Five patients were receiving therapy with the hypoglycemic agent glibenclamide, five were on NPH insulin and five were on dietary therapy alone. When compared to controls, the latter two groups had intact gonadotropin responses to LHRH. Despite normal basal gonadotropin levels, however, the group receiving glibenclamide therapy showed significantly exaggerated LH and FSH responses to LHRH. Both basal PRL and TSH levels, as well as the responses to TRH were normal in all three groups. These results indicate that LH, FSH, TSH and PRL secretion is intact in uncomplicated diabetes mellitus. The exaggerated LH and FSH responses to LHRH in the glibenclamide treated subjects are probably related to primary gonadal involvement; alternatively, there may be augmented pituitary gonadotropin secretion in this group.     

Effect of non aromatizable androgens on LHRH and TRH responses in primary testicular failure

We have assessed the gonadotropin, TSH and PRL responses to the non aromatizable androgens, mesterolone and fluoxymestrone, in 27 patients with primary testicular failure. All patients were given a bolus of LHRH (100 micrograms) and TRH (200 micrograms) at zero time. Nine subjects received a further bolus of TRH at 30 mins. The latter were then given mesterolone 150 mg daily for 6 weeks. The remaining subjects received fluoxymesterone 5 mg daily for 4 weeks and 10 mg daily for 2 weeks. On the last day of the androgen administration, the subjects were re-challenged with LHRH and TRH according to the identical protocol. When compared to controls, the patients had normal circulating levels of testosterone, estradiol, PRL and thyroid hormones. However, basal LH, FSH and TSH levels, as well as gonadotropin responses to LHRH and TSH and PRL responses to TRH, were increased. Mesterolone administration produced no changes in steroids, thyroid hormones, gonadotropins nor PRL. There was, however, a reduction in the integrated and incremental TSH secretion after TRH. Fluoxymesterone administration was accompanied by a reduction in thyroid binding globulin (with associated decreases in T3 and increases in T3 resin uptake). The free T4 index was unaltered, which implies that thyroid function was unchanged. In addition, during fluoxymesterone administration, there was a reduction in testosterone, gonadotropins and LH response to LHRH. Basal TSH did not vary, but there was a reduction in the peak and integrated TSH response to TRH. PRL levels were unaltered during fluoxymesterone treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ontogeny of pituitary gonadotrophin secretion in the fetal and post-natal pig in response to LHRH in vitro

Monolayer cultures of anterior pituitary cells from male or female pigs of 60, 80, 105 days of fetal life or of 60, 160 and 250 days of post-natal life were prepared and treated with LHRH (1 pM to 10 nM). Dose-related increases of LH were first seen at 80 days of gestation in both sexes, while only female fetuses responded to maximal LHRH at 60 days. Basal and stimulated LH release doubled in cultures from 105-day-old fetuses when compared with those at 80 days. Compared to late fetal stages LH release was 20- to 30-fold higher in cell cultures from 60-day-old (post-natal) donors without further change during the post-natal period. In all pre- and post-natal age groups basal and maximal LH release of pituitary cells from males was lower than that of females. FSH stimulation started in male and female cells at 80 days of gestation only at LHRH concentrations exceeding or equal to 0.1 nM. By 105 days FSH secretion was dose-related and pituitary cells of females responded with higher FSH values than did those of males. In general, post-natal cells released much higher amounts of FSH than did prenatal cells. Basal and maximal release of FSH decreased during post-natal development in both sexes. Basal as well as maximal FSH release of cultures from female donors was higher than that found in cultures from male donors. Determination of total LH and FSH content in fetal pituitary cell cultures indicated that the developmental increase in gonadotrophin release potential is a function of the total gonadotrophin content in vitro. We conclude that (1) the in-vitro release of gonadotrophins to LHRH is dose-, age- and sex-dependent; (2) in the female fetal pig LH responsiveness develops earlier than FSH responsiveness; (3) apparently, these maturational changes mainly reflect alterations in pituitary gonadotrophin content; and (4) there is no simple relationship between in-vitro release and circulating gonadotrophins.     

A case with isolated ACTH deficiency accompanying chronic thyroiditis

An unusual case of isolated ACTH deficiency with coexisting chronic thyroiditis in a 53-year-old man is reported. The patient was admitted with a 2-year history of generalized fatigue, a 13-kg weight loss, muscular weakness, and frequent hypotensive and hypoglycemic attacks. On admission serum thyroxine and triiodothyronine were significantly elevated. Basal TSH concentration was not detected and TSH showed no response to TRH, but one month after replacement therapy with hydrocortisone it was shown that serum T3, T4 and TSH response were all within normal limits. Thyroid antibodies were positive and biopsy of the thyroid gland showed chronic thyroiditis. Arginine and 1-Dopa provoked a subnormal rise in GH with a maximum of 5.6 ng/ml and 5.0, respectively. One month after treatment with hydrocortisone, GH response to 1-Dopa and arginine increased to the normal range. Prolactin response to TRH was normal and FSH response to LHRH was also normal. LH showed an exaggerated response to LHRH, although a normal response was revealed after treatment with hydrocortisone. We also presented a summary of 44 Japanese cases, 23 males (mean age; 46 yrs old) and 21 females (mean age; 48 yrs old), with isolated ACTH deficiency.     

Influence of synthetic thyrotropin-releasing hormone tartrate monohydrate on plasma gonadotropin concentration of normal males.

Synthetic thyrotropin-releasing hormone (TRH) tartrate monohydrate was administered by rapid intravenous injection to nine normal males. Plasma thyroid-stimulating hormone (TSH), luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were measured before and at selected periods after TRH injection. The mean plasma TSH value immediately prior to TRH injection was 3.5 muU/ml and the level 15 min after injection was 14.8 muU/ml. The mean plasma LH value immediately prior to TRH injection was 8.0 mIU/ml and the level 15 min after injection was 15.0 mIU/ml. The latter elevation was statistically significant (p less than 0.01), although it was just above the upper normal range. The mean plasma FSH value immediately prior to TRH injecion was 7.7 mIU/ml, and a significant difference was not observed after TRH administration. These results revealed that synthetic TRH tartrate monohydrate influenced the release of LH from the anterior pituitary.     

Hormonal responses to female conspecifics in hyperprolactinemic male rats and mice

Exposure to a female results in an acute release of LH and testosterone (T) in normal male rats and mice. This study was conducted to determine whether these hormonal responses are altered in hyperprolactinemic (hyperPRL) male rats in which copulatory behavior is known to be suppressed and in hyperPRL male mice in which it is not. Adult male CDF (F-344) rats were made hyperPRL either by grafting of three anterior pituitaries under the kidney capsule or by treatment with diethylstilbestrol (DES). Exposure of control males to receptive females for 10-15 min produced the expected two- to fourfold statistically significant elevations in plasma LH levels. In contrast, plasma LH levels in pituitary grafted or DES-treated males were not altered by female exposure. Male mice were pituitary grafted (two pituitaries per recipient) or sham-operated and housed individually with a female for 1 week. The resident females were then replaced with novel females in half of the cages and blood samples were taken from the males after 5 min exposure for determination of LH levels or after 45-60 min exposure for T levels. Female-induced LH and T elevations occurred in both hyperPRL and control groups. Failure of hyperPRL male rats to experience an increase in plasma LH levels in response to a female suggests abnormality of mechanisms controlling LHRH release. Suppression of LHRH release may be involved also in the induction of deficits of sexual behavior in these animals.     

Effect of bombesin on basal and stimulated secretion of some pituitary hormones in humans

The effect of bombesin (5 ng/kg/min X 2.5 h) on basal pituitary secretion as well as on the response to thyrotropin releasing hormone (TRH; 200 micrograms) plus luteinizing hormone releasing hormone (LHRH; 100 micrograms) was studied in healthy male volunteers. The peptide did not change the basal level of growth hormone (GH), prolactin, thyroid-stimulating hormone (TSH), luteinizing hormone (LH) and follicle-stimulating hormone (FSH). On the contrary, the pituitary response to releasing hormones was modified by bombesin administration. When compared with control (saline) values, prolactin and TSH levels after TRH were lower during bombesin infusion, whereas LH and FSH levels after LHRH were higher. Thus bombesin affects in man, as in experimental animals, the secretion of some pituitary hormones.     

Prospective study on the influence of radiochemotherapy on pituitary function in children with acute leukaemia and NHL.

To assess effects of chemo- and radiotherapy on the endocrine system 31 children with acute leukaemia and NHL (3 AML, 24 ALL, 4 NHL) were investigated. Children were treated according to modified BFM protocols. 25 patients were before, 5 during and one after puberty (2 to 16 y.). Before treatment, during induction therapy, during cranial irradiation, 4-6 weeks later and during maintenance therapy the following hormone values were estimated: TSH and prolactin basal and 30 min. after TRH (5 micrograms/kg i.v.), LH and FSH basal. Final investigations included total T4 and T3. In conclusion, chemo- und radiotherapy lead to transient elevations of TSH and prolactin in a few patients, but without proof for permanent disorders. Due to the fact all 3 patients with hyperprolactinaemia showed high prolactin levels (700 to 770 mU/l) already before treatment it is unlikely therapy was the main cause of these observed alterations. Although basal LH and FSH values were in normal ranges for age the increasing values after cranial irradiation in prepubertal children may reflect a possible initiation of early maturation, reported by others. Furthermore a retrospective growth study was performed in children treated with 2 different protocols. Protocol LSA2L2 used in the past before 1981 resulted in a permanent reduction of the height. In contrast, the mean SDS for height in children treated with protocol VII declined only during the intensive period of treatment. A catch-up growth occured already during maintenance therapy. Prophylactic cranial irradiation with 18 Gy in our patients under protocol LSA2L2 did not affect growth during the first 5 years after diagnosis.     

Effects of a long-acting LHRH agonist preparation on plasma gonadotropin and prolactin levels in castrated male rats and on the release of prolactin from ectopic pituitaries

We have examined the effects of a single subcutaneous injection of an LHRH agonist, D-Trp-6-LHRH, in biodegradable microcapsules of poly(DL-lactide-co-glycolide) on plasma gonadotropin and prolactin (PRL) levels in castrated and in castrated-hypophysectomized-pituitary grafted (CAST-APX-GRAFT) male rats. The results were compared to the effects of daily injections of the same LHRH agonist dissolved in saline. In castrated rats, there were no significant alterations in plasma LH or PRL levels during the 10 days following the injection of LHRH agonist microcapsules, while FSH levels were generally reduced. In castrated males given daily injections of 6 micrograms of LHRH agonist in saline, plasma LH levels were significantly reduced while plasma PRL levels were not changed. In CAST-APX-GRAFT rats, both D-Trp-6-LHRH microcapsules and daily LHRH agonist injections appeared to increase plasma PRL levels. The pattern of changes in PRL release in both groups was similar, with levels on day 6 being significantly higher than those measured on days 1, 3 and 10 after onset of treatment. As expected, LH and FSH levels in these animals were extremely low. Immunoreactive D-Trp-6-LHRH was consistently detectable in the plasma of CAST-APX-GRAFT animals after microcapsule administration, whereas in animals given daily injections of this agonist in saline, its plasma concentrations were often below the detectability limit of the employed assay. These findings suggest that the LHRH agonist, D-Trp-6-LHRH, is capable of causing a short term stimulation of PRL release from ectopic pituitaries. Elevation of plasma LH levels is apparently not required for this effect.     

Pharmacodynamic tests of the stimulation of hypophyseal function: simplification of the procedure without alteration of their diagnostic value

The aim of this study was to examine if it was possible to simplify the procedure of some stimulation tests of pituitary function. This study was performed on 300 stimulation tests of TSH by TRH, PRL by TRH, LH by LHRH and FSH by LHRH, respectively. Simplified procedures may be proposed without altering the diagnostic value of the tests: assay of TSH and PRL 0 and 30 minutes after TRH injection and of LH and FSH 0, 30 and 60 minutes after LHRH injection.     

Plasma androgen and gonadotropin levels during hibernation and testicular maturation in golden-mantled ground squirrels

The 4-5-mo hibernation season of golden-mantled ground squirrels consists of extended torpor bouts interspersed with brief, periodic intervals of normothermic arousal. Plasma levels of testosterone (T), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) and degree of scrotal pigmentation were measured in torpid and aroused male ground squirrels throughout a season of hibernation and in active animals after the termination of torpor. T was basal in torpid animals; beginning 3 weeks before torpor ended, T was elevated in normothermic males during the first half of periodic arousals but returned to basal levels before animals reentered torpor. After the last (terminal) arousal from torpor, T levels were moderately elevated for 4 wk and maximal for the next 6 wk before they returned to basal values. LH patterns were similar to those of T; however, levels of T and LH were positively correlated only in aroused or posthibernation males. FSH levels remained constant and low during most of the heterothermic season but increased in several torpid males within 3 days of terminal arousal. FSH levels peaked 2 wk after the end of heterothermy. Scrotal pigmentation developed over the first 4 wk after terminal arousal. Maturation of reproductive function occurs during the 4 wk after termination of heterothermy, but elevated levels of T during arousals and variable levels of FSH in the last days of torpor suggest that activation or increased sensitivity of the hypothalamic-pituitary-gonadal axis is important in the termination of heterothermy in ground squirrels.     

Effects of luteinizing hormone releasing hormone on gonadotrophins in the hamster

The changes in serum gonadotrophins in male hamsters following one injection of 15 μg luteinizing hormone releasing hormone (LHRH) (Group A) were compared with those following the last injection of LHRH in animals receiving an injection approximately every 12 hr for 4 days (Group B) or 12 days (Group C). Peak follicle stimulating hormone (FSH) levels (ng/ml) were 1776±218 (Group A), 2904±346 (Group B), and 4336±449 (Group C). Peak luteinizing hormone (LH) values (ng/ml) were 1352±80 (Group A), 410±12 (Group B), and 498±53 (Group C). Serum FSH:LH ratios, calculated from the concentrations measured 16 hr after the last LHRH injections, were higher in Groups B and C than in Group A. Similar injections of LHRH (100 ng or 15 μg/injection) for 6 days elevated the serum FSH:LH ratio in intact males. Five such LHRH injections (100 ng/injection) blunted the rise in serum LH in orchidectomized hamsters. Direct effects of LHRH on gonadotrophin secretory dynamics or altered brain-pituitary-testicular interactions may alter the ratio of FSH to LH in the hamster.     

Effects of complete hypothalamic deafferentation on the estrous phase of follicle-stimulating hormone release in the cyclic rat

We investigated whether neural afferents to the medial basal hypothalamus play an acute role in the estrous phase of FSH release in the 4-day cyclic rat. A cannula was inserted into the right atrium of the heart under brief ether anesthesia during the early afternoon of proestrus for subsequent blood collections and injection of LHRH. In some of the rats, the medial basal hypothalamus was surgically isolated from the rest of the brain with a small knife under brief ether anesthesia between 2000 h and 2130 h of proestrus. Control groups consisted of naive rats which were not treated during the night of proestrus and sham-operated animals in which the knife was lowered to the corpus callosum between 2000 h and 2130 h or proestrus. Rats were bled at 2200 h of proestrus and at 0200 h, 0600 h and 1000 h of estrus for radioimmunoassay of plasma FSH and LH. The plasma FSH levels in all 3 groups between 2200 h of proestrus and 1000 h of estrus were elevated above levels observed in other cannulated rats bled to the onset of the proestrous phase of FSH release at 1400 h of proestrus. There were no statistically significant differences in plasma FSH or LH concentrations at any of the time periods between the 3 groups of serially bled rats. The deafferentation procedure did not appear to impair the pituitary gland's ability to secret gonadotrophins as injection of 50 ng of LHRH after the bleeding at 1000 h of estrus caused substantial elevations in plasma FSH and LH concentrations which were not different between the 3 groups. The results suggest that neural afferents to the medial basal hypothalamus play no acute role in the estrous phase of FSH release in the cyclic rat.     

The effects of porcine follicular fluid inhibin on gonadotropin secretion in the rabbit

Porcine follicular fluid (pff), treated with charcoal to remove steroids, was used to determine whether inhibin is active in the laboratory rabbit. When pff (5 ml/4 kg body weight) was injected (ip) into does that had been castrated 2 weeks earlier, there was a significant decline in blood follicle-stimulating hormone (FSH) levels; the decline lasted for 8-12 h. Blood levels of luteinizing hormone (LH) were suppressed, but only briefly at 3 h after injection. In other experiments, intact does which had been injected with pff 9 h and 10 min before receiving a single, i.v. injection of luteinizing hormone-releasing hormone (LHRH) (10 micrograms/kg body weight) showed a sharp reduction in the concentration of LH in the blood samples collected 15, 30 and 60 min after LHRH administration. Secretion of FSH responded poorly to LHRH stimulation, and pff had little suppressive action on blood levels. Having established that the pff preparation had inhibin activity, its action on the postovulatory surge of FSH secretion was next examined. This release of FSH, which occurs 6 to 36 h after ovulation, has been hypothesized to be required for the establishment of pregnancy by stimulating the growth of the ovarian follicles supplying the luteotropic estradiol. To test this hypothesis, pff was injected into rabbits every 8 h for the first 5 days of pregnancy and found to block the postovulatory FSH surge. The patterns of secretion of LH and progesterone in the same pff-injected animals were, however, not altered from normal pregnancy patterns by pff.(ABSTRACT TRUNCATED AT 250 WORDS)     

Studies on the effects of low doses of 5 alpha-dihydrotestosterone (DHT) on the basal levels of serum gonadotropins and the sensitivity of the pituitary to luteinizing hormone releasing hormone (LHRH) in adult male rats

Investigations were undertaken to study the effect of administering s.c. 10, 25, 50, 100, 500 and 1000 ng DHT/rat/day to normal adult male rats, for six weeks, on the basal levels of serum gonadotropin and the sensitivity of the pituitary to LHRH. The control group received olive oil. Animals were weighed and bled via cardiac puncture before the beginning of the treatment and weekly thereafter. After the last bleeding rats were injected intracardially 200 ng LHRH/rat and killed 15 min later. Blood, pituitary and testes were collected. Data were analyzed with respect to the control group and with respect to day zero of the treatment. DHT failed to produce a persistent effect on the serum gonadotropin. 10 and 500 ng DHT suppressed FSH levels significantly on days 21 and 7, respectively. 25, 50, 100 and 1000 ng DHT stimulated the release of FSH on day 42. 10 ng DHT reduced the levels of LH on day 14 of the treatment. 10, 25 and 50 ng DHT increased the sensitivity of the pituitary to release more LH in response to LHRH while 100, 500, 1000 ng DHT inhibited LHRH induced release of FSH. DHT at all doses tested failed to affect intrapituitary levels of LH and FSH. 10, 500 and 1000 ng DHT reduced the weights of the pituitaries as compared to the control group. The data demonstrate effects of DHT which are transient on the basal release of gonadotropins but are more persistent and differential on the sensitivity of the pituitary to LHRH.     

Effects of hypothalamic neurohormones on prolactin release from pituitary allografts in the hamster

Recent reports indicate that luteinizing hormone-releasing hormone (LHRH) releases prolactin (PRL) under some circumstances. We examined the chronic effects of LHRH, growth hormone-releasing hormone (GHRH), and corticotrophin-releasing hormone (CRH) on the release of PRL, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) by pituitary allografts in hypophysectomized, orchidectomized hamsters. Entire pituitary glands removed from 7-week-old-male Golden Syrian hamsters were placed under the renal capsule of hypophysectomized, orchidectomized 12-week-old hamsters. Beginning 6 days postgrafting, hamsters were injected subcutaneously twice daily with 1 microgram LHRH, 4 micrograms GHRH, or 4 micrograms CRH in 100 microliter of vehicle for 16 days. Six hosts from each of the four groups were decapitated on Day 17, 16 hr after the last injection. Prolactin, LH, and FSH were measured in serum collected from the trunk blood. Treatment with LHRH significantly elevated serum PRL levels above those measured in the other three groups, which were all similar to one another. Serum LH levels in hosts treated with vehicle were elevated above those measured in the other three groups. Serum FSH levels in hosts treated with LHRH were greater than FSH levels in any of the other three groups. These results indicate that chronic treatment with LHRH can stimulate PRL and FSH release by ectopic pituitary cells in the hamster.