Metabolic clearance and secretion rates of TSH following adrenalectomy and corticosterone administration in the rat.

Abstract

Male rats were either bilaterally adrenalectomized or injected twice-daily with corticosterone (675 μg/lOO g), procedures found to result respectively in enhancement or depression of ACTH secretion, reflected by a 150% increase of the pituitary ACTH concentration 1 month after adrenalectomy and by a 50% decrease of this parameter associated with pronounced adrenal atrophy after 2 weeks of corticosterone administration. The pituitary TSH level was not affected by these procedures, whereas the plasma TSH concentration was significantly higher in the adrenalectomized than in the corticosterone- treated animals. The plasma TSH concentrations recorded at progressively longer time intervals after the iv injection of a uniform dose of TSH or of its vehicle and respectively corresponding to “total” and to “endogenous” levels provided the basis for evaluation of the disappearance characteristics of the “exogenous” hormone by analytical (regression) and numerical (trapezoidal rule) techniques of integration. Regres...