The relationship between body weight and thyroid hormone levels is complex. It is known that higher body weight and body mass index (BMI) is linked to higher blood levels of TSH and lower levels of free thyroxine (FT4). This pattern is typically seen in hypothyroidism, where TSH levels are high and the FT4 levels are low. However, T3 levels are often higher in obesity and high T3 levels are seen in hyperthyroidism. Weight gain is common in hypothyroidism while weight loss is common in hyperthyroidism.
Thyroid hormone levels also change during pregnancy, as both TSH and FT4 levels frequently lower while T3 levels are higher. It is unknown what the correlation is between obesity and pregnancy in terms of thyroid hormone levels. This study looked at thyroid tests during pregnancy and their link with the mother’s weight both before and during pregnancy.
THE FULL ARTICLE TITLE:
M Collares F. Maternal thyroid function, prepregnancy obesity and gestational weight gain— the Generation R Study: a prospective cohort study. Clin Endocrinol (Oxf ). June 30, 2017 [Epub ahead of print].
SUMMARY OF THE STUDY
This study was done in Rotterdam, Netherlands. About 5,000 patients were studied during pregnancy (on average at14 weeks of pregnancy). Blood levels of TSH and FT4 were examined to see if there was a link with the weight and BMI before pregnancy and weight gain during pregnancy.