What is the study about?The thyroid gland controls the body's energy levels. In hypothyroidism, energy levels slow down and patients frequently gain weight. This is assumed to be an increase in the body fat mass, as opposed to muscle mass (lean body mass). Treatment with thyroid hormone returns energy levels to normal and often results in some degree of weight loss, again the decrease is thought to be from the body fat mass. Hypothyroid patients also retain fluid and thyroid hormone treatment increases fluid excretion. Total body fluid is accounted for when muscle mass is measured. This study was performed to discover how weight loss occurs during the treatment of hypothyroidism by measuring changes in fat mass and muscle mass.
Possible mechanisms of weight loss during treatment of hypothyroidism
Clinical Thyroidology for Patients - Heather Hofflich, MD
What was the aim of the study?The goal of this study was to determine the cause of weight changes associated with hypothyroidism.
Who was studied?Participants in the study were referred to the Endocrine clinic in Denmark and were newly diagnosed with autoimmune hypothyroidism (Hashimoto's thyroiditis). There were 12 patients included in this study.
How was the study done?Each participant had a physical examination, measurement of body composition (fat and muscle mass) and resting energy levels. They had their physical activity levels evaluated before starting thyroid medication and again periodically over 1 year. Thyroid function levels were measured (TSH and free T4) to check their thyroid function at baseline and at 1 year. They measured physical activity levels with a questionnaire and pedometers.
Weight Loss after Therapy of Hypothyroidism Is Mainly Caused by Excretion of Excess Body Water Associated with Myxoedema
Karmisholt J et al., J Clin Endocrinol Metab 2010