Circadian variations in blood glucose, plasma insulin and human growth hormone response were studied in six healthy males who received 100 gm. oral glucose loads at 6 a.m., noon, 6 p.m., and midnight. The tests were conducted at seven day intervals, and each was preceded by a ten hour fast. During the three days before each test the subjects received meals containing no less than 300 gm. carbohydrate per day. Blood samples were drawn at 0, 15, 30, 60, 90, 120, and 180 minutes. A clear circadian variation occurred in the blood glucose levels, with lower values in the morning and higher values at 6 p.m. and midnight. The insulin profiles showed a trend toward lower afternoon and night values, with a noon peak. The afternoon insulin-glucose ratios were significantly lower. HGH values were inconsistent and tended toward higher afternoon and night basal levels. The results confirm the existence of a circadian variation in the blood glucose response to oral glucose loads in healthy men. This might in turn result from a circadian variation in the insulin response, probably secondary to changes in the pancreatic β cell sensitivity to glucose. This basic mechanism is believed to sustain the conditioning influence of other hormones, HGH being one of them.

The effect of acute and chronic administration of sulpiride sulphate on serum prolactin levels in humans was studied. Six normal women and four normal men received an i.m. injection of 100 mg sulpiride at 0800 h. A control group received saline solution 0.9%. Blood samples were taken before and 30, 60 and 120 minutes after the injection. Serum prolactin was determined by a double antibody radioimmunoassay technique. Sulpiride induced in all subjects a quick and marked increment of serum prolactin levels with peak values at 30 minutes. At 120 minutes the levels remained high. In another experiment six post menopausal women received 150 mg of sulpiride orally during 10 days. Five of them had marked increments of circulating levels of prolactin at the end of treatment. It is suggested that sulpiride could be used in the dynamic functional exploration of hypothalamic-pitutiary system.

No abstract

The responses of FSH, LH and testosterone to acute stimulation with synthetic LRF were studied in 6 healthy, fertile men aged 33.4 plus or minus 1.6 yr (X plus or minus SE). Fifty mug of LRF were given, iv at 0600 h, 1200 h, 1800 h and 0000 h, at 1-week intervals, to all 6 volunteers simultaneously. Blood samples were collected by venipuncture before (-5 and 0 min) and 8, 16, 32, 64 and 128 min after LRF injection. Plasma levels of FSH, LH and testosterone were determined by double antibody radioimmunoassay techniques. The responses of FSH and LH to LRF injection showed a clear difference at the times studied. Maximal values were obtained at 0600 h and 1800 h while the response at noon was not significant for LH and absent for FSH. Testosterone secretion showed a clear-cut response to LRF in all the subjects. At three of the four studied times (0600 h, 1800 h, 000 h) plasma testosterone was already increased at 8 min reaching its maximum at 16 min and persisted high until the end of the study. The noon response reached its maximum at the end of the test period. The daily variations of FSH and LH responses to acute LRF stimulation should be taken into consideration in clinical practive and the increment in testosterone secretion makes this test a useful indicator for androgenic testicular reserve.