Euthyroid sick syndrome (ESS) is characterized by abnormal thyroid function tests, most notably a low triiodothyronine (T3) level, occurring in the absence of intrinsic thyroid disease. A 54-year-old woman presented to the endocrinology clinic with a 4-month history of progressive fatigue, lethargy, and new-onset cold intolerance after initiation of semaglutide for weight management. The dose was titrated monthly over 4 months, during which she experienced significant weight loss of 22 kg. Laboratory evaluation revealed a thyroid function profile classic for ESS, with low free T3, low-normal free T4, and a normal thyroid-stimulating hormone (TSH) level that was inappropriately low relative to the reduced T3. After exclusion of primary thyroid and pituitary disorders, a diagnosis of ESS secondary to the catabolic state induced by rapid weight loss was made. The patient was counseled that this represented a physiological adaptation rather than intrinsic thyroid disease. Semaglutide was continued given its metabolic benefits, and nutritional optimization with adequate caloric and protein intake was advised.
Elmezayen et al. (Wed,) studied this question.