Plasma Prolactin in Normal and Hypertensive Subjects: Relationships with Age, Posture, Blood Pressure, Catecholamines, and Renin*

It has been suggested that patients with essential hypertension have hyperprolactinemia, and that the disturbances in blood pressure and PRL may be secondary to abnormal central dopaminergic regulation. Interrelations between plasma PRL and age, posture, blood pressure, plasma and urinary electrolytes, PRA, and catecholamine excretion rates were studied in 27 normal subjects and 23 patients with essential hypertension. In normal subjects, upright plasma PRL correlated inversely with age; mean levels were significantly higher below the age of 40 yr than in older persons [8.1 ± 1.1 vs. 4.4 ± 0.6 (SEM) ng/ml; P < 0.005]. No significant age-PRL relationship was found in supine normal man or in essential hypertension. Assumption of upright posture slightly increased circulating PRL levels from 7.3 ± 1.0 to 10.1 ± 1.7 ng/ml (P < 0.01) in hypertensive but not in normal subjects (from 7.4 ± 0.7 to 6.9 ± 0.8 ng/ ml). Thus, the upright plasma PRL levels tended to be mildly elevated in essential hypertension (P < 0.05), but supine values were normal. Relationships between plasma PRL and blood pressure or pressor correlates such as plasma renin or norepinephrine excretion rate either were not significant or were significantly inverse in the two populations. It is concluded that circulating PRL, either directly or indirectly as an index of central dopaminergic activity, does not play an important pathogenic role in maintaining essential hypertension. Moreover, the data suggest that age and posture should be considered in the interpretation of plasma PRL measurements.