Failure of endogenous prolactin to alter renal salt and water excretion and adrenal function in man

Prolactin is a salt-retaining hormone in fish, and a similar role is frequently postulated in man, although clinical observation does not generally support this. The effect of TRH induced acute elevation of endogenous serum prolactin on renal water, sodium, potassium and total solute excretion was investigated during metabolic balance conditions and during escape from mineralocorticoid excess in 8 normal volunteers (6 males, 2 females). Cortisol and aldosterone production was additionally assessed by measuring plasma cortisol and aldosterone and urinary 17-hydroxysteroid, 17-ketosteroid and aldosterone excretion. No significant effect on renal water and solute handling was observed in any subject. Repetitive prolactin stimulation did not change the results. It is concluded that, in adult man, acute changes in serum prolactin do not alter salt and water metabolism or adrenal function.