Prolactin response to arginine in children with hyperthyroidism and primary hypothyroidism

Plasma prolactin (PRL) response to arginine was examined in 16 prepubertal and 18 pubertal children with constitutional short stature, 5 patients with hyperthyroidism and 4 patients with primary hypothyroidism. The mean basal concentration of plasma PRL was significantly higher (P less than 0.01) in primary hypothyroidism than in other groups. Arginine infusion elicited significant (P less than 0.05) rises in plasma PRL in all groups. The maximal increment of plasma PRL above the baseline level after arginine stimulation was significantly larger (P less than 0.05) in pubertal than in prepubertal females and was significantly smaller (P less than 0.05) in patients with hyperthyroidism than in age- and sex-matched controls. There was no sex difference in arginine-stimulated PRL secretion. These data suggest that arginine produces a significant increase in plasma PRL and the PRL response to arginine was greater in pubertal than in prepubertal children. Plasma PRL response to arginine is suppressed in children with hyperthyroidism and the basal plasma PRL is markedly elevated in primary hypothyroidism.