Thyroid function and perimenopausal lipid and weight changes: the Thyroid Study in Healthy Women (TSH-W)

We designed a prospective observational trial to study the relationship of thyroid function to cholesterol and weight changes at menopause. Subjects were participants in the ongoing Healthy Women Study, a prospective study of cardiovascular risk factor change through menopause. Healthy premenopausal women were recruited from a random sample of licensed drivers in selected ZIP codes of Allegheny County, Pennsylvania. Participants had to be 42-50 years of age, have menstruated within the last 3 months, not have had surgical menopause, have diastolic blood pressure < 100 mm Hg, and not be taking medications (including insulin, estrogen, lipid-lowering drugs, or thyroid or antihypertensive medications) at the baseline examination. The substudy included three groups of women who were premenopausal at baseline and were categorized according to change noted at follow-up regarding menopausal status and use of hormone replacement therapy (HRT). The groups comprised 95 women who remained premenopausal, 96 postmenopausal women not on HRT, and 61 postmenopausal women using HRT. The main outcome measures were baseline and follow-up measurements for serum levels of thyroid-stimulating hormone (TSH), thyroid peroxidase, and thyroglobulin, as well as serum cholesterol, total high-density lipoprotein (HDL) cholesterol, triglycerides, and calculated low-density lipoprotein (LDL) cholesterol, height, and weight. Covariates included cigarette smoking and alcohol intake. The prevalence of thyroid antibodies in this healthy population was high at both time points (range 27%-31%) and did not differ by menopausal status. The presence of thyroid antibodies was associated with increased TSH concentration. Women with antibodies at both time points had lower levels of total and LDL cholesterol compared with those with no antibodies, significant only for those women who remained premenopausal during the follow-up period. Thyroid function during menopause in this healthy population is unlikely to account for the observed changes in levels of serum lipoprotein and body weight. The presence of thyroid antibodies may be associated with lower total and LDL cholesterol, possibly through an underlying inflammatory disorder.