Thyroid hormone increases mannan-binding lectin levels.
BACKGROUND
Recent studies have indicated the existence of causal links between the endocrine and immune systems and cardiovascular disease. Mannan-binding lectin (MBL), a protein of the innate immune system, may constitute a connection between these fields.


METHODS
To test whether thyroid hormone regulates MBL levels, we studied eight patients with Graves' hyperthyroidism before and after methimazole therapy, eight healthy subjects before and after short-term experimental hyperthyroidism, and eight hypothyroid patients with chronic auto-immune thyroiditis before and after L-thyroxine substitution.


RESULTS
In all hyperthyroid patients, MBL levels were increased--median (range), 1886 ng/ml (1478-7344) --before treatment and decreased to 954 ng/ml (312-3222) after treatment (P = 0.01, paired comparison: Wilcoxon's signed ranks test). The healthy subjects had MBL levels of 1081 ng/ml (312-1578). Administration of thyroid hormones to these persons induced mild hyperthyroidism and increased MBL levels significantly to 1714 ng/ml (356-2488) (P = 0.01). Two of the eight hypothyroid patients had undetectably low levels of MBL both before and after L-thyroxine substitution. The other six hypothyroid patients had decreased levels of MBL of 145 ng/ml (20-457) compared with 979 ng/ml (214-1533) after L-thyroxine substitution (P = 0.03, paired comparison: Wilcoxon's signed ranks test).


CONCLUSIONS
Our data show that thyroid hormone increases levels of MBL. MBL is part of the inflammatory complement system, and this modulation of complement activation may play a role in the pathogenesis of a number of key components of thyroid diseases.
Riis
Anne Lene Dalkjaer
AL
Medical Department M, Aarhus University Hospital, Denmark. anne.lene.riis@ki.au.dk
Hansen
Troels Krarup
TK
Thiel
Steffen
S
Gravholt
Claus Højbjerg
CH
Gjedde
Signe
S
Gormsen
Lars Christian
LC
Jørgensen
Jens Otto Lunde
JO
Weeke
Jørgen
J
Møller
Niels
N
D000328:Adult; D013956:Antithyroid Agents / Q000627:therapeutic use; D005260:Female; D006111:Graves Disease / Q000097:blood* / Q000188:drug therapy; D006801:Humans; D006980:Hyperthyroidism / Q000097:blood* / Q000139:chemically induced; D007037:Hypothyroidism / Q000097:blood*; D008297:Male; D037601:Mannose-Binding Lectin / Q000097:blood*; D050606:Mannose-Binding Protein-Associated Serine Proteases / Q000378:metabolism; D008713:Methimazole / Q000627:therapeutic use; D008875:Middle Aged; D016037:Single-Blind Method; D013963:Thyroid Hormones / Q000494:pharmacology*; D013967:Thyroiditis, Autoimmune / Q000097:blood*; D013974:Thyroxine / Q000494:pharmacology; D014284:Triiodothyronine / Q000494:pharmacology
D013956:Antithyroid Agents; D037601:Mannose-Binding Lectin; D013963:Thyroid Hormones; D014284:Triiodothyronine; D008713:Methimazole; C105296:MASP2 protein, human; D050606:Mannose-Binding Protein-Associated Serine Proteases; D013974:Thyroxine