Do you have autoimmune thyroid disease? In what month were you born?
(I assume that the months would be shifted by 6 in the southern hemisphere. )
Clin Endocrinol (Oxf). 2017 Jul 20. doi: 10.1111/cen.13425. [Epub ahead of print]
Month of birth is associated with the subsequent diagnosis of autoimmune hypothyroidism. A nationwide Danish register-based study.
Thvilum M1, Brandt F2, Brix TH1, Hegedüs L1 .
Author information:
1 Department of Endocrinology and Metabolism, Odense University Hospital, Denmark. Kloevervaenget 10, 6th floor, 5000, Denmark.
2 Department of Internal Medicine, Hospital of Southern Denmark, Sydvang 1, 6400, Sonderborg, Denmark.
Abstract
BACKGROUND:
The triggering of thyroid autoimmunity in the genetically susceptible remains a conundrum. Environmental exposures during gestation and/or early postnatally have proponents, as suggested in diabetes mellitus, with a higher incidence of births during spring and summer. Whether the development of autoimmune hypothyroidism (AIT) is influenced by month or season of birth is less clear.
METHOD:
Nationwide cohort study of 111,565 individuals diagnosed with AIT and four euthyroid controls per case, matched according to age and sex, were identified from Danish health registers. Differences in month-of-birth across the year was evaluated by the Walter-Elwood test. The risk of AIT patients being born in a certain month or season of the year was calculated using a Cox regression model.
RESULTS:
There was a significant difference in birth month between cases and controls, p<0.001. Individuals with AIT had a significantly increased risk of being born in June (Hazard ratio 1.04; 95% Confidence interval (CI): 1.02-1.08) and in the summer (June-August; HR 1.02; 95%CI: 1.01-1.04).
CONCLUSION:
In this large-scale nationwide cohort study, we found a higher risk of AIT when born in the summer season or more specifically in June, supporting the hypothesis that seasonal variations in exposures - gestationally and/or early postnatally - may contribute to the development of AIT. This article is protected by copyright. All rights reserved.
PMID: 28727153