SHORT-TERM VARIATION IN BLOOD LEVELS OF PROLACTIN, LUTEINIZING HORMONE AND FOLLICLE-STIMULATING HORMONE IN NORMAL MEN THROUGHOUT THE DAY

Abstract

The release of prolactin may be related to that of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) (Bern & Nicoll, 1968). The present study was designed to determine whether there is any relationship between the short-term variation in blood LH and FSH levels (Naftolin, Yen & Tsai, 1972; Nankin & Troen, 1972), and that of prolactin levels in the blood. A total of 230 blood samples were obtained from five normal men (age 24–29) at 15-min intervals between 09.00 and 16.30 h. All subjects continued their normal daily routine during the experiment. Samples were collected through an indwelling Polythene cannula, and the plasma was separated and stored at −20 °C. Prolactin levels were determined by radioimmunoassay (McNeilly, 1973). The results are expressed as ng standard human pituitary prolactin (kindly provided by Dr H. Friesen)/ml. Serum LH and FSH were measured by double-antibody radioimmunoassay as described by McNeilly & Chard (1974).