Thyroid hormone secretion rates: response to endogenous and exogenous TSH in man during surgery.
The thyroid hormone secretory response to TSH was studied in twenty-eight patients undergoing thyroid and parathyroid surgery. Eighteen patients received bovine or human exogenous TSH by injection into a thyroid artery, and 10 received TRH to stimulate endogenous TSH secretion. Thyroid secretion rates of T4, T3, and rT3 were determined directly from measurement of blood flow and the hormone gradient across the gland. A significant secretory response was seen for all three hormones following TSH increase. T3 secretion accelerated more rapidly than that of T4 and rT3, thus reducing the T4/T3 and rT3/T3 ratios. The T4/rT3 ratio fell during the first 30 min but then increased. The responses correlated with the area under the curve of the TSH serum concentration, and were similar after administration of bovine and human exogenous TSH, and TRH. Conclusions regarding preferential secretion ought to be made by comparing ratios of thyroid hormone secretion with those of the hormone content of the gland, but our results indicate that TSH induces preferential secretion of triiodothyronines in man.
D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D006961:Hyperparathyroidism / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D012636:Secretory Rate; D013961:Thyroid Gland / Q000503:physiopathology*; D013963:Thyroid Hormones / Q000378:metabolism*; D013965:Thyroidectomy; D013972:Thyrotropin / Q000378:metabolism / Q000494:pharmacology*; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology; D013974:Thyroxine / Q000378:metabolism; D014284:Triiodothyronine / Q000378:metabolism; D014285:Triiodothyronine, Reverse / Q000378:metabolism
D013963:Thyroid Hormones; D014284:Triiodothyronine; D014285:Triiodothyronine, Reverse; D013973:Thyrotropin-Releasing Hormone; D013972:Thyrotropin; D013974:Thyroxine