Thyrotropin N-glycosylation and Glycan Composition in Severe Primary Hypothyroidism.

The majority of TSH molecules in severe primary hypothyroidism were less N- glycosylated, more sialylated, and less sulfonated compared with euthyroid individuals. This glycan pattern favors a prolonged half-life in the circulation combined with lower in vitro biopotency at the target cells. During levothyroxine treatment of sPH patients, the sialylation and sulfonation of glycans were restored already at low FT4 levels, while N-glycosylation of TSH was not restored until the FT4 levels were normal.