Recovery of pituitary thyrotropic function after withdrawal of prolonged thyroid-suppression therapy.
The pattern of thyrotropin secretion was analyzed in seven euthyroid women, before and after withdrawal of long-term thyroid hormone, by serial measurements of thyroid 131l uptake, serum thyroxine, tri-iodothyronine, and thyrotropin concentrations, and the response to thyrotropin-releasing hormone. During exogenous hormone administration, 131l uptake was suppressed, and serum thyrotropin concentrations before and after administration of thyrotropin-releasing hormone were undetectable. After withdrawal of exogenous hormone, thyrotropin secretory function was transiently impaired, as indicated by undetectable basal thyrotropin concentrations together with absence of response to thyrotropin-releasing hormone, and subsequently by normal values of basal thyrotropin concentration and normal responses to releasing hormone while serum thyroxine and tri-iodothyronine concentrations were subnormal. Decreased thyrotropin reserve persisted for two to five weeks. Detectable values of serum thyrotropin (less than 1.2 muU per milliliter) and a normal 131l uptake usually occurred concurrently in two to three weeks. Serum thyroxine concentration returned to normal at least four weeks after hormone withdrawal.
D000328:Adult; D000368:Aged; D005260:Female; D006042:Goiter / Q000188:drug therapy; D006801:Humans; D008875:Middle Aged; D013375:Substance Withdrawal Syndrome; D013962:Thyroid (USP) / Q000494:pharmacology / Q000627:therapeutic use; D013963:Thyroid Hormones / Q000494:pharmacology*; D013972:Thyrotropin / Q000097:blood / Q000378:metabolism*; D013973:Thyrotropin-Releasing Hormone; D013974:Thyroxine / Q000097:blood / Q000494:pharmacology / Q000627:therapeutic use; D014284:Triiodothyronine / Q000097:blood
D013962:Thyroid (USP); D013963:Thyroid Hormones; D014284:Triiodothyronine; D013973:Thyrotropin-Releasing Hormone; D013972:Thyrotropin; D013974:Thyroxine