In 50 healthy women and 57 healthy men aged 20--80 years serum-prolactin-levels before and after intravenous injection of 200 micrograms TRH were measured and correlations with serum-triglycerid-, sodium-, basal TSH and serum insulin levels as well as sodium concentration of red blood cells, age, relativ body weight (Broca) and blood pressure were calculated. In men of different age no changes in basal serum-prolactin-levels can be detected. In 60--80 years old men a significant higher but later occuring TRH-induced prolactin secretion than in younger men can be found. 50--59 year old women have a significant higher prolactin secretion after TRH application than 20--29 year old females. Basal serum prolactin levels of women correlate negative significant with serum sodium levels and positive significant with the sodium concentration of red blood cells and basal TSH values. Relative prolactin out-put (prolactin-max--prolactin-basal) after TRH-application in women is found to correlate positiv significant with serum triglycerid levels. In men relative prolactin out-put following TRH-injection correlates negativ significant with basal serum insulin levels. This correlation diminishes when age and Broca are kept constant in the calculation.