Metabolic Clearance and Production Rates of Human Thyrotropin

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Abstract

Metabolic clearance (MCR) and production rates (PR) of human thyrotropin (hTSH) were determined by the constant infusion to equilibrium method 57 times in 55 patients. 16 control patients had a mean hTSH MCR of 50.7 ml/min. The mean hTSH MCR was significantly (P < 0.02) higher in 19 euthyroid men (51.6 ml/min) than in 12 euthyroid women (43.0 ml/min), but this apparent sex difference disappeared when the MCR were corrected for surface area, 25.8 (men) versus 25.2 ml/min per m2 (women). Hypothyroid patients had significantly (P < 0.005) lower hTSH MCR (30.9 ml/min), and hyperthyroid patients had significantly (P < 0.05) higher hTSH MCR (60.9 ml/min) than controls. The hTSH MCR in patients with “decreased thyroid reserve” (40.9 ml/min), hyperfunctioning thyroid nodule (53.8 ml/min), and “empty sella syndrome” (46.6 ml/min) were not significantly different from controls. The mean hTSH PR in controls (104.3 mU/day) was significantly (P < 0.005) different from that in patients with “decreased thyroid reserve” (956 mU/day), hypothyroidism (4,440 mU/day), hyperthyroidism (< 43.9 mU/day) and a hyperfunctioning thyroid nodule (< 38.7 mU/day). In primary hypothyroidism intravenous triiodothyronine therapy (50 μg/day) for 10 days decreased the hTSH PR (from 4,244 to 2,461 mU/day) before changes in the hTSH MCR (from 33.1 to 33.7 mU/day) were observed.

Authors

E. Chester Ridgway, Bruce D. Weintraub, Farahe Maloof