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Homologous radioimmunoassay of human prolactin was performed and used to investigate the secretion of this pituitary hormone under normal and pathological conditions. The following data were developed in this paper: --During the menstrual cycle, prolactin levels are more elevated during ovulatory and luteal phases than during follicular phase; --During pregnancy, prolactin levels progressively increase to reach their maximum at the end of gestation; --During lactation, prolactin levels increase for the two days following delivery, then progressively decrease; --Bromocryptine oral administration drastically reduces prolactin levels within the 24 hours as it inhibits the prolactin release normally induced by suckling. Assays of prolactin is useful to define the role of this hormone in the genesis of the galactorrhea. Bromocryptine as L Dopa reduce the hyperprolactinemia either functional or tumoral in origin. TRH provokes prolactin release which is more pronounced in females than in males. Pituitary prolactin reserve may be appreciated in several pathological conditions. It appears to be of first interest to assess the residual function of the pituitary gland after surgical removal of adenoma. Depuis 1971, la prolactine humaine peut être dosée dans les milieux biologiques par méthode radio-immunologique (G. BRYANT et coll., 1971; M. L'HERMITTE et coll., 1972; H. FRIESEN et coll., 1972; SINHA et coll., 1973). En 1974 nous avons proposé une méthode de dosage radio-immunologique homologue (A. REUTER et coll., 1976). Grâce à celle-ci nous avons exploré la sécrétion de cette hormone hypophysaire dans certaines conditions normales et pathologiques.

The excretion of immunoreactive and radioactive material in urine was studied after intravenous injection of synthetic LH-RH in a rabbit and in a man. The LH-RH-like immunoreactive substance (LHRH-LIS) found in unextracted urine by radioimmunoassay was excreted within the same timelag and in the same proportions in the rabbit and in the human, but different from those of synthetic LH-RH, as shown by purifications on sephadex.

The existence of endogenous LH RH like immunoreactivity is shown in human urines after appropriate extraction, bu the radioimmunoassay of LH RH. In normaly cycling and menopausal women the quantities of endogenous hormone found in urines are greater after acid extraction than those found after extraction at pH 7. Furthermore, the increase observed by extraction in acidified methanol is directly correlated and proportional to the quantity of hormone assayable by extraction at pH 7. The hypothesis of urinary excretion of LH RH as a polymer of immunoreactive units is suggested by this study.

A method of extraction of synthetic LHRH is studied in human urines, using porous glass (Spherosil) and methanol. In the defined conditions the yield is greeter than 80%. It appears that the method is reproducible. The recovery varies essentially with the quantity of Spherosil and the pH of methanal. The use of methanol acidified at pH 3 increases the speed and the importance of labelled LHRH recovery.