Natural history of the transition from euthyroidism to overt autoimmune hypo- or hyperthyroidism: a prospective study.
OBJECTIVE
To evaluate the progression in time from euthyroidism to overt autoimmune hypothyroidism or to overt autoimmune hyperthyroidism.


METHODS
The design is that of a nested case-control study within the prospective Amsterdam autoimmune thyroid disease (AITD) cohort study in which 790 healthy euthyroid women with at least one first or second degree relative with documented AITD were followed for 5 years. Thyroid function tests were assessed annually. Contrast between cases (overt hypothyroidism - TSH>5.7 mU/l and free thyroxine (FT(4))<9.3 pmol/l and overt hyperthyroidism - TSH<0.4 mU/l and FT(4)>20.1 pmol/l, also referred to as events) and controls (matched for age and duration of follow-up).


RESULTS
At baseline, the 38 hypothyroid cases had already higher TSH and lower FT(4) concentrations than their 76 controls, and the difference between both the groups persisted 1 year before occurrence of the event. In contrast, neither TSH nor FT(4) values differed between the 13 hyperthyroid cases and their 26 controls at baseline or 1 year before the event. The prevalence of thyroid peroxidase-Ab was higher in both hypothyroid and hyperthyroid cases than in controls. At the time of event, hypothyroid cases were less common among current smokers (P=0.083) and more common in the postpartum period (P=0.006) than their controls, whereas hyperthyroid cases were pregnant more frequently (P=0.063).


CONCLUSIONS
The data suggest that progression toward overt autoimmune hypothyroidism is a gradual process taking several years, but in contrast overt autoimmune hyperthyroidism develops faster in terms of months.
Departments of Endocrinology and Metabolism Cardiology, Academic Medical Centre, University of Amsterdam, PO Box 22700, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands. grigoris.effraimidis@gmail.com
Grigoris
G
Effraimidis
Thea G A
TG
Strieder
Jan G P
JG
Tijssen
Wilmar M
WM
Wiersinga
D000328:Adult; D000368:Aged; D001323:Autoantibodies / Q000097:blood*; D015551:Autoimmunity; D016022:Case-Control Studies; D018450:Disease Progression; D005260:Female; D020022:Genetic Predisposition to Disease; D006111:Graves Disease / Q000276:immunology; D050031:Hashimoto Disease / Q000276:immunology; D006801:Humans; D006980:Hyperthyroidism / Q000209:etiology / Q000235:genetics / Q000276:immunology*; D007037:Hypothyroidism / Q000209:etiology / Q000235:genetics / Q000276:immunology*; D007455:Iodine / Q000008:administration & dosage*; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D050032:Postpartum Thyroiditis / Q000276:immunology; D011247:Pregnancy; D011446:Prospective Studies; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*; D016540:Smoking Cessation; D013997:Time Factors
D001323:Autoantibodies; D007455:Iodine