Effect of naloxone on TRH-induced PRL and TSH response in normal man.

The effect of naloxone on PRL and TSH response to TRH was studied in 8 normal men. PRL response to TRH was unaffected by the administration of naloxone. TSH response to TRH was significantly decreased by naloxone, considering the maximum absolute increment (p less than 0.01) and the areas under curves (p less than 0.05). In conclusion, the PRL response to TRH may be unaffected by endogenous opioids or naloxone and we were unable to reveal a possible opioid effect in our experimental conditions. TSH response to TRH seems to be affected by endogenous opioids, possibly due to an indirect or direct action on TRH and/or on the pituitary.

Differences in cortisol, aldosterone and testosterone responses to ACTH 1-17 administered at two different times of day.

The effects of 100 micrograms, i.m. of the analog ACTH 1-17 administered at 0800 and 1800 on the secretion of cortisol, aldosterone and testosterone have been studied in normal subjects: 8 male and 8 female. The group as a whole and the males had significantly greater absolute and percent increments in plasma cortisol after administration at 1800. In the females, there was only a greater percent increment in cortisol after the evening administration. The heptadecapeptide always significantly stimulated serum aldosterone, with no difference between the two times of administration. In the females, ACTH 1-17 significantly stimulated testosterone, with a more protracted secretion after the evening administration. In the males, there was always a significant testosterone decrease after the administration of the drug, with no difference between morning and evening. In conclusion, 100 micrograms i.m. of the analog ACTH 1-17 stimulates cortisol secretion more when given during the circadian nadir of plasma cortisol, but only in men. ACTH 1-17 increases testosterone in women and decreases it in men, whereas it seems to increase aldosterone secretion in both sexes.