Mode of action of carbimazole in Graves' disease.
In a series of hyperthyroid subjects treated with a high dose 'block-replace' regime, mean thyroidal technetium uptake was shown to fall progressively over an 18 month period. Furthermore, sub-total inhibition of hormone biosynthesis could be demonstrated, without evidence of proportionate inhibition of organification, the regression of radio-iodine on technetium thyroid uptake showing similar slopes in euthyroid, treated and untreated hyperthyroid subjects. Together with the reported differential in remission rates between propranolol and anti-thyroid drugs, it is concluded that carbimazole does not act solely by inhibiting intrathyroid hormono-genesis, but more definitively by affecting thyroid hyperstimulation at a pre-biosynthetic level. The inability to demonstrate normal suppressibility of trapping in any subject in the present series despite extended therapy with a 'block-replace' regime, further suggests that current concepts of 'suppressibility' are invalid, the progressive fall in technetium uptake being unlikely to represent spontaneous restoration of a normal pituitary-thyroid axis, but rather a direct influence or prolonged therapy with anti-thyroid drugs on the natural history of the disease.
D000293:Adolescent; D000328:Adult; D002231:Carbimazole / Q000494:pharmacology / Q000627:therapeutic use*; D005260:Female; D006111:Graves Disease / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D006801:Humans; D008297:Male; D013667:Technetium; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology
D013667:Technetium; D002231:Carbimazole