Affiliation:
1. Department of Medical Sciences, Uppsala University, Clinical Chemistry, University Hospital, Uppsala, Sweden
Abstract
Abstract
Context
In severe primary hypothyroidism (sPH), the serum thyrotropin (TSH) levels are elevated with an increased degree of sialylation. The circulating TSH comprises 2 different TSH glycoforms: TSHdi with 2 and TSHtri with 3 N-glycans and methods have developed to determine their contents of anionic monosaccharides (AMS), that is, sialic acid (SA) and sulfonated N-acetylglactosamine (SU) residues.
Objective
Characterize N-glycosylation and glycan composition of circulating TSH molecules and determine the effects during levothyroxine treatment in patients with sPH.
Methods
Serum samples were obtained from 25 patients with sPH, from 159 euthyroid individuals, and from 12 women during treatment with levothyroxine for sPH. Degrees of N-glycosylation and concentrations of TSHdi and TSHtri as well as their contents of AMS, SA, and SU residues were determined.
Results
The circulating TSH molecules in sPH patients had lower degrees of N-glycosylation, higher degrees of sialylation, and lower degrees of sulfonation than in euthyroid individuals. Levothyroxin restored sialylation and sulfonation of the glycans already at low free thyroxine (FT4) levels, while degree of N-glycosylation was not restored until the FT4 levels were normal.
Conclusions
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.
Subject
Endocrinology, Diabetes and Metabolism
Cited by
5 articles.
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