Circadian time structure of pituitary and adrenal response to CRF, TRH and LHRH.

In six healthy males, aged 25.3 +/- 0.66, the pituitary and adrenal simultaneous response to CRF (1 microgram/kg), TRH (200 micrograms) and LH-RH (100 micrograms) was studied at the following times of different days: 0400, 0800, 1200, 1600, 2000 and 0000. Each test was preceded by a 8-hr fast after a meal containing 600 cal (CHO 50%, lipid 30%, protein 20%). The interval between two consecutive tests was 52 hrs and the starting time was randomized. The serum cortisol was measured before and after 60, 120, 180, 240 min. Serum TSH, Prolactin, FSH and LH were measured before and after 5, 10, 15, 30, 60, 90 and 120 min. The statistical analysis was reported by both mean chronograms (as absolute values and relative change or absolute difference from mesor) and mean cosinor on basal values and total (T.A.) or incremental (I.A.) areas after RH stimulus. Serum cortisol: a statistically significant circadian rhythm was found for basal values with a peak in the morning (phi at 1040; 95% C.L. 0808-1438). T.A. after RH stimulus as well appeared statistically higher again in the morning, whereas the I.A. presented an opposite phase with higher values at night (phi at 2133; 95% C.L. 2055-0312). Serum Prolactin: mean chronogram analysis showed significantly higher basal values at 0800 and lower values at 1600, whereas I.A. were significantly lower in the morning. Serum LH: basal values were statistically higher in the morning, while T.A. and I.A. showed an opposite behaviour with peaks in the night (T.A.: phi at 2015, 95% C.L. 1710-0035; I.A.: 0 2033; 95% C.L. 1736-0004).(ABSTRACT TRUNCATED AT 250 WORDS)