Childhood Weight Gain and Thyroid Autoimmunity at Age 60–64 Years: The 1946 British Birth Cohort Study

BACKGROUND: Complex bidirectional relationships have been described between body weight, thyroid function, and risk of thyroid disorders, including thyroid autoimmunity. We used a life-course approach to examine the potential association of childhood or adult body weight with the risk of thyroid autoimmunity and other thyroid disorders at age 60–64 years in a large population-based birth cohort study. METHODS: In the UK Medical Research Council 1946 British Birth Cohort study, at age 60–64 years, 1277 women and 1185 men (78% of the target sample) responded to a postal questionnaire, which included questions on thyroid disease and thyroid medication. Circulating antithyroid peroxidase antibodies, free T(4), and TSH concentrations were measured in 1057 women and 997 men at a subsequent clinic visit. Birth weight was recorded, and height and weight were measured at ages 2, 4, 6, 7, 11, 15 years and also repeatedly in adulthood. RESULTS: At age 60–64 years, 10.9% of women (139 of 1277) and 2.3% of men (27 of 1185) reported they were taking T(4), and 11.5% of women (122 of 1057) and 3.3% of men (33 of 997) had positive anti-TPO antibodies (>100 IU/mL), consistent with thyroid autoimmunity. Among women, both T(4) use and positive anti-TPO antibodies at age 60–64 years were positively associated with childhood body weight, childhood overweight, and adult body mass index. Childhood weight gain between 0 and 14 years of age was positively associated with later T(4) use (odds ratio 1.21, 95% confidence interval 1.03–1.42) and positive anti-TPO antibodies (1.21, 1.00–1.47). Women who were overweight or obese at age 14 years (127 of 972) had a higher risk of later positive anti-TPO antibodies (2.05, 1.12–3.76). In men and women without any thyroid disorders, serum free T(4) concentrations were inversely associated with concurrent body mass index (P = .002). CONCLUSIONS: Childhood weight gain and childhood overweight conferred an increased susceptibility to later hypothyroidism and thyroid autoimmunity, particularly in women.