[Alterations of the thyroid function in patients with morbid obesity]

The morbid obesity (BMI greater than or equal to 40 kg/m2) is associated with dysfunction of the hypothalamus-pituitary-thyroid axis, showing high levels of thyrotropin (TSH), triiodothyronine (T3) total and free, suspecting a real thyroid condition. Our objetive was to describe the alterations in thyroid function in patients with morbid obesity, determining serum levels of TSH, total T3, free T4 and thyroid peroxidase antibodies (TPO).

Prospective, descriptive, observational, cross-sectional study, we enrolled 52 patients with morbid obesity, at the obesity clinic, from department of Endocrinology, since January 2009 to July 2011. All patients signed a letter of informed consent. Patients with known thyroid disorders and/or under the use of levothyroxine or other medication that causes alteration in thyroid function were excluded. Statistical analysis was performed using measures of central tendency, simple frequencies, percentages and Spearman's correlation.

The prevalence of primary hypothyroidism was 8%, 6% subclinical hypothyroidism and thyroid function alterations secondary to obesity of 23% (elevated TSH and/or free T4 Total T3 with normal and TPO antibody negative).

Most morbidly obese patients haven't autoimmune thyroid dysfunction; the alterations in thyroid function are caused by an effect of homeostasis against obesity and can be corrected by reducing weight.