SELECTIVITY OF THE EFFECTS OF HYPOTHALAMIC LESIONS ON PITUITARY TROPHIC HORMONE SECRETION IN THE RAT1

IN THE rat, hypothalamic lesions may result in testicular atrophy (1, 2, 3), disturbances of the estrus cycle (4, 5), and “goiter block” (impairment of the hyperplastic-hypertrophic thyroid response to goitrogen treatment) (6, 3, 7, 8, 9). These effects have been interpreted as sequelae of depressed gonadotrophin and thyrotrophin secretion (3, 5, 7, 8). Although such lesions may appear virtually to abolish gonadotrophin secretion, producing a degree of testicular atrophy approaching that found after hypophysectomy, they have not (in the rat) been found to eliminate thyrotrophin secretion completely (8, 9). Evidence that they may depress corticotrophin secretion severely enough to permit marked atrophy of the adrenal cortex has not been abundant, but this effect has been noted also (8, 10). Further observations on lesion-induced adrenal atrophy are included in the present report.