Propranolol and thyroid hormone metabolism.
Propranolol decreases plasma T3 and increases plasma rT3 in a dose-dependent manner due to a decreased production rate of T3 and a decreased metabolic clearance rate of rT3, respectively, caused by inhibition of the conversion of T4 into T3 and of rT3 into 3,3'-T2. This inhibition of 5'-deiodination is not secondary to inhibition of thyroid hormone transport across the plasma membrane. Propranolol and its major metabolite, 4-hydroxypropranolol, are not directly responsible for these effects, but an unidentified metabolite of propranolol might be involved. beta-blockers ameliorate clinical symptoms and signs of thyrotoxicosis independent of the decrease of plasma 13, that is confined to beta-blockers with membrane-stabilizing activity, such as propranolol and alprenolol. The decrease of plasma T3, however, appears responsible for some of the metabolic responses to beta-blockers.
Wiersinga
W M
WM
Department of Endocrinology, Academisch Medisch Centrum, Amsterdam, The Netherlands.
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D006801:Humans; D007037:Hypothyroidism / Q000188:drug therapy; D008657:Metabolic Clearance Rate; D011433:Propranolol / Q000494:pharmacology*; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism; D013963:Thyroid Hormones / Q000378:metabolism*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
D000319:Adrenergic beta-Antagonists; D013963:Thyroid Hormones; D014284:Triiodothyronine; D013972:Thyrotropin; D011433:Propranolol; D013974:Thyroxine