Parity and 11-year serum thyrotropin and thyroid autoantibody change: A longitudinal population-based study.

Parity and 11-year serum thyrotropin and thyroid autoantibody change: A longitudinal population-based study.

Thyroid. 2015 Dec 29;

Authors: Bjergved L, Carlé A, Jørgensen T, Perrild H, Laurberg P, Krejbjerg A, Ovesen L, Bülow Pedersen I, Rasmussen LB, Knudsen N

Abstract
Background A role for female reproductive factors in the pathogenesis of thyroid autoimmunity has been suggested. We investigated the prospective association between parity, abortion, use of oral contraceptive pill (OCP), and use of hormone replacement therapy (HRT), and 11-year change in serum thyrotropin (TSH) as well as change in thyroid peroxidase autoantibody (TPO-Ab) status. Methods A random sample of 4,649 persons aged 18-65 years participated in a population-based study in the period 1997-1998. In the study presented here, we included 1,749 non-pregnant women with no history of thyroid disease who participated in the 11-year follow-up examination in the period 2008-2010. Gynecological exposures were reported in a self-administered questionnaire at baseline and follow-up. TSH and TPO-Ab were measured at baseline and follow-up. Increased TPO-Ab status during follow-up was defined as a TPO-Ab below assay cut-off (< 30 kU/L) at baseline and TPO-Ab ≥ 30 kU/L at follow-up. Multiple linear regression models were used, adjusted for age, smoking status, and urinary iodine excretion. Results An inverse association was found between the number of years on hormone replacement therapy and the risk (odds ratio) of increased TPO-Ab status during follow-up (0.735 (95% confidence interval, CI 0.558, 0.968), P=0.03). This association was however not statistically significant when applying the Bonferroni adjusted significance level. The remaining reproductive factors showed no statistically significant association with risk of increased TPO-Ab during follow-up. Also, parity, abortions, use of OCP, HRT use, age at menarche and being pre- or postmenopausal were not significantly associated with 11-year TSH change. Conclusions We found no statistically significant association between the studied female reproductive measures and 11-year risk of TSH or TPO-change. A possible protective role for hormone replacement therapy in the etiology of thyroid autoimmunity however deserves further research.

PMID: 26711373 [PubMed - as supplied by publisher]

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