title: Dynamics of serum rT3 and 3,3'-T2 during rT3 infusion in patients treated for thyrotoxicosis with propylthiouracil or methimazole.
abstract: rT3 metabolism in patients treated for thyrotoxicosis with prophylthiouracil (PTU), or methimazole (MMI) was studied by infusion of rT3 and measurements of the increase in serum rT3 and serum 3,3'-diiodothyronine. The results indicate that the high serum rT3 observed during treatment with PTU is not due to an increase in rT3 production, but to a decrease in the metabolic clearance rate of rT3. rT3 infusion was followed by an increase in serum 3,3'-T2 which was similar whether PTU or MMI was given. However, after stopping rT3 infusion there was a more rapid fall serum 3,3'-T2 during MMI treatment, compatible with an inhibitory effect of PTU on 3,3'-T2 degradation.
mesh_terms: D000328:Adult; D000368:Aged; D004104:Diiodothyronines / Q000097:blood*; D005260:Female; D006801:Humans; D006980:Hyperthyroidism / Q000097:blood* / Q000188:drug therapy; D008297:Male; D008713:Methimazole / Q000627:therapeutic use; D008875:Middle Aged; D011441:Propylthiouracil / Q000627:therapeutic use; D013970:Thyronines / Q000097:blood*; D014284:Triiodothyronine / Q000097:blood*; D014285:Triiodothyronine, Reverse / Q000097:blood*
chemical_list: D004104:Diiodothyronines; D013970:Thyronines; D014284:Triiodothyronine; D008713:Methimazole; D014285:Triiodothyronine, Reverse; D011441:Propylthiouracil