Lack of inhibitory effect of exogenous prolactin on ovarian responsiveness to gonadotropins in the rat

Attempts were made to elucidate the possible antigonadotropic action of PRL at the ovarian level. Immature female rats of Wistar strain were injected subcutaneously with PMS (5-10 i.u.) at 0900 h on day 23 of age, followed an intraperitoneal injection of HCG (5-10 i.u.) at 1400 h on day 25. In all animals treated with PMS-HCG, ova were found in the oviducts when examined at 0900 h on day 26 of age. Rat PRL was administered either at various doses (1.0-20 micrograms/day) in the morning (0800 h) between day 23-25 or at 5 micrograms/day for 10 days prior to HCG injection. The ability of exogenous gonadotropins to induce ovulation and weight gain of the ovary were not affected by this PRL treatment. In animals injected with PMS, significant rises in serum estradiol-17 beta levels were observed 48 h later. This PMS-induced increase in the estrogen concentration was also not affected by the treatment with various doses of PRL. From these results, it seems likely that exogenously administered PRL may be unable to suppress the ovarian responsiveness to gonadotropins by direct action on the ovary.

An acute increase in serum prolactin does not modify gonadotropin release in female rats

Attempts were made to find out whether hyperprolactinemia has an effect on the hypothalamo-pituitary response to estrogen feedback and LHRH stimulation. Adult female rats of Wistar strain were ovariectomized and received subcutaneous injection of 20 micrograms estradiol benzoate (EB) 3-4 weeks later (day-0). A second injection of 20 micrograms EB, when administered at noon on day-3, induced a highly significant increase in serum LH (p less than 0.001 vs. basal values), but not FSH, estimated at 1800 h on the same day. This EB-promoted LH release was not altered by pretreatment with rat PRL (5 micrograms/day), which was administered subcutaneously daily in the morning (1100 h) between day-1 and day-3. No statistical difference in the serum LH concentration was found when compared with the values for the control animals pretreated with 0.9% saline alone. Serum gonadotropins 15 min after LHRH administration (100 ng/100 g BW) in 32-day-old female rats were not statistically different between the animals pretreated with 5 micrograms PRL, which was given subcutaneously daily (at 0800 h) for 3 days, and the controls pretreated with 0.9% saline. These results suggest that an acute increase in serum PRL may not exert a negative effect on the gonadotropin release induced by estrogen feedback and LHRH stimulation.

[Evaluation of hypothalamic-pituitary function in amenorrheic women by utilizing the combined clomiphene-GnRH test (author's transl)]

Hypothalamic-pituitary function in 62 women with amenorrhea syndrome was evaluated by comparing the response of gonadotropin to GnRH stimulation before and after clomiphene treatment. Each woman was initially tested with an intramuscular injection of 100 microgram GnRH, and then ingested 150 mg of clomiphene daily for 5 consecutive days followed by GnRH test. Fourteen out of 29 patients with 1st grade amenorrhea showed increased baseline LH, FSH and estradiol, and slightly decreased net responses of LH to GnRH after clomiphene administration, indicating that positive and negative estrogen feedback for gonadotropin release is functioning. In contrast, 8 patients with 2nd grade amenorrhea (17 cases) showed an increase in LH net responses after Clomid treatment. In 5 patients, however, clomiphene induced the increase in baseline LH and FSH values and the decrease in the LH release in response to GnRH as seen in the 1st grade amenorrheic patients. These 5 patients ovulated on that clomiphene dosage. One patient with PCO also had a barely significant decrease in LH responses to GnRH following clomiphene administration, with slightly increased baseline gonadotropins. With one exception, all the 5 patients with primary amenorrhea showed no or poor LH responses to GnRH. Following clomiphene administration, no change in either baseline gonadotropine levels or pituitary responsiveness to GnRH was observed in 4 patients, suggesting that a hypothalamic-pituitary defect appeared most likely to be present. The two patients with streak gonad had significantly high responses to GnRH injection and further increase in the responses following clomiphene administration, accompanied by a slightly decreased baseline gonadotropin levels. On the other hand, in hyperprolactinemic amenorrhea syndrome individual response to GnRH before and after clomiphene use was quite variable. It is likely that this group includes the patients with various pathologic states of the hypothalamic-pituitary system. Thus, syndrome and in diagnosing the degree and the site of the defect.

[A simplified method for measuring the binding capacity of sex hormone-binding globulin in human serum and its clinical application (author's transl)]

A simple and reliable method for determining the binding capacity of the sex hormone-binding globulin (SHBG-BC) in human serum is described. The principle of this method is to saturate the SHBG binding sites with dihydrotestosterone (DHT) and measure the amount of SHBG-bound steroid. Endogenous steroids are initially removed from the serum samples by adsorption on dextran-coated charcoal. The samples are subsequently equilibrated with a mixture of known amount of tritium-labeled and unlabeled DHT. The unbound steroid is removed by dextran-coated charcoal incubated at 4 degrees C, and the mass of bound DHT is determined from the known specific activity of the added steroid. The intraassay and interassay coefficient of variation of this assay method is less than 6.2% and 7.5%, respectively. Forty serum samples can be assayed in duplicate in a working day. The mean values of SHBG-BC, expressed as microgram DHT bound per 100ml serum, were 1.56 +/- 0.33 (SD) in 6 adult men aged 20 approximately 40 and 2.05 +/- 0.75 in 37 adult women aged 20 approximately 36. Higher levels (1.75 +/- 0.40) were found in 10 older men aged 65 approximately 80. In contrast, SHBG-BC (1.80 +/- 0.30) in postmenopausal women (ages 52 approximately to 62) was lower than that in the reproductive age group of women. No significant variations in SHBG-BC were observed during the normal menstrual cycle. The levels of SHBG-BC rose progressively in pregnancy to 9 approximately 10 times those in the normal non-pregnant women. In 4 women with polycystic ovarian disease and 2 hirsute women, SHBG-BC levels were lower (means: 1.63 and 0.75, respectively), while patients with 1st and 2nd grade amenorrhea showed levels similar to those in the reproductive women.

[Effects of several estrogenic compounds on serum corticosteroid-binding globulin (CBG) and the estrogen thresholds for increasing CBG (author's transl)]

The effects of several estrogen substances--alone, or in combination with norgestrel--on serum CBG in humans are reported in this paper. CBG was measured by a modified charcoal adsorption technique. Daily oral doses of Premarin, from 0.3 to 2.5mg, were given to healthy postmenopausal women for 14 days. Dose-dependent increases in CBG-BC were observed. Ovral, which contains ethinylestradiol and norgestrel, also induced significant increases in the levels of CBG-BC. Similar results were seen with Lo Ovral, but it had less influence than Ovral. When given alone, daily for 21 days, norgestrel had no effect on CBG-BC. The maximum rise of serum CBG-BC was found after 10 days of the daily doses of Ovral, and then the levels remained quite constant during the period of treatment. Exogenous estrogens of other types also caused increases in CBG-BC. The response of CBG to exogenous estrogens is of use in comparing the estrogen potencies of the compounds. CBG-BC levels remained constant throughout the menstrual cycle in five normal women despite fluctuating levels of estradiol which reached peaks of 190 approximately 430 pg/ml. In pregnant women and in HMG-treated women, however, serum levels of CBG-BC increased beginning when estradiol levels were greater than 1 ng/ml.

[A double adsorption technique for the determination of corticosteroid-binding globulin in human serum (author's transl)]

Despite the widespread use of many different estrogenic compounds in hormonal contraception and estrogen replacement, in the human a simple test for comparing the potencies of the compounds is lacking. Many of the estrogenic compounds are difficult to measure, and animal studies may not relate directly to those done on humans in terms of potency. Corticosteroid-binding globulin (CBG) in human serum has been known since 1958 to increase in response to estrogen administration, and the degree of its elevation has been shown to be closely dose-related and reasonably sensitive. Therefore, CBG represents a biological parameter that provides for the specific quantal analysis of estrogenicity in the human. In this paper a simple and reliable method for the determination of the cortisol-binding capacity of CBG (CBG-BC) in human serum is described. The procedure is based on the amount of cortisol required to saturate the CBG binding sites. All endogenous steroids are initially removed from the serum by adsorption on dextran-coated charcoal (DCC). A mixture of a known amount of unlabeled and labeled cortisol is added to the sample in order to saturate the "stripped" binding sites of CBG. The unbound cortisol is removed by DCC at 4 degrees C, and the supernatant represents the total cortisol-binding capacity of the serum sample. To distinguish between cortisol-binding to CBG and to albumin, "stripped" serum is heated for 30 min at 60 degrees C, the temperature which does not influence cortisol binding by albumin but which does inactivate CBG. The samples are subsequently equilibrated with a mixture of labeled and unlabeled cortisol. The free cortisol is removed by DCC and the bound cortisol remaining in the supernatant is designated as the albumin-bound cortisol. Thus, CBG-BC is assayed by a double adsorption technique as differential binding to native and heat-inactivated serum. The cortisol determined by this method corresponds to CBG-bound cortisol, and CBG-BC is expressed as micrograms of cortisol bound per 100 ml serum. The precision and accuracy of the method were found to be good. The values of CBG-BC obtained by this method were 14.9 +/- 1.9 (SD) microgram/100ml in adult men and 16.0 +/- 1.8 microgram/100ml in adult women. Daily serum samples in five women revealed no significant variations in CBG-BC throughout the normal menstrual cycle despite fluctuating levels of serum estradiol. CBG-BC was also found not to vary significantly with age. In pregnancy, however CBG-BC increased significantly.

Radioimmunoassay of serum medroxyprogesterone acetate (Provera) in women following oral and intravaginal administration

A radioimmunoassay (RIA) method for measuring medroxyprogesterone acetate (MPA, Provera) in serum has been developed utilizing benzene:iso-octane extraction, 3H-MPA to assess procedural losses, goat anti-MPA-3-(0-carboxymethyl) oxime-bovine serum albumin serum and dextran-coated charcoal separation. Control serum blanks were undetectable, 200 pg/ml of MPA was measurable with a high reliability, and intra- and interassay coefficients of variation were 6 and 13 percent, respectively. MPA added to control serum was quantitatively recovered. Serum MPA levels measured in 2 women after ingestion of 10 mg MPA rose to 3.4 to 4.4 ng/ml within 1 to 4 hours after oral intake and fell rapidly thereafter to 0.3 to 0.6 ng/ml within 24 hours. Insertion of Silastic intra-vaginal rings (IVRs), containing 100 or 200 mg of MPA, into 4 women for periods of 3 weeks resulted in a rapid rise of serum MPA after insertion, rather stable MPA levels of 0.9 to 1.6 ng/ml while the IVRs were in place, and a rapid decline of serum MPA following IVR removal. Serum estradiol-17beta and progesterone concentrations, measured about 3 times a week in these patients, indicated that ovulation was consistently inhibited. The serum MPA levels observed in this study were approximately 5 times lower than those reported by other investigators using a double-antibody RIA of MPA in unextracted serum.