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HÈLÈNE MARCEAU, ALFONSO DELGADO, BARBARA MACINTOSH-HARDT, CLAUDE FORTIER, Metabolic Clearance and Secretion Rates of TSH Following Adrenalectomy and Corticosterone Administration in the Rat, Endocrinology, Volume 90, Issue 4, 1 April 1972, Pages 973–980, https://doi.org/10.1210/endo-90-4-973
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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. Regression allowed characterization of a onecompartment model and analysis of the metabolic clearance rate (MCR) in terms of the halflife of the hormone and of a virtual volume of distribution approximating that of plasma. Numerical integration, which yielded unbiased and probably more realistic estimates of the MCR, revealed highly significant and opposite effects of adrenalectomy (depression) and of corticosterone administration (increase) of this parameter. The TSH secretion rate, corresponding to the product of the MCR by the resting hormonal concentration, was not affected by withdrawal or administration of adrenal cortical hormones and the consequent opposite alterations of ACTH secretion. This evidence does not support the hypothesis of a competition between either CRF and TRF at the hypothalamic level, or between ACTH and TSH at the hypophysial level. (Endocrinology90: 973, 1972)
