Endocr Connect. 2023 Aug 1:EC-23-0314. doi: 10.1530/EC-23-0314. Online ahead of print.
ABSTRACT
CONTEXT: In individuals with hypothyroidism and overweight, levothyroxine substitution therapy is often expected to cause weight loss due to its effect on resting energy expenditure. However, despite levothyroxine-induced enhancement of resting energy expenditure, fat mass loss is rarely seen after levothyroxine substitution therapy. The mechanism behind this conundrum is unknown.
OBJECTIVE: To assess the effect of levothyroxine therapy on hunger sensations and ad libitum food intake in individuals with hypothyroidism.
DESIGN AND SETTING: Prospective cohort study of 18 newly diagnosed hypothyroid women (thyroid-stimulating hormone (TSH) >10 mU/L). Participants were investigated at diagnosis, after normalization of TSH (<4.0 mU/L), and after six months of successful treatment. Eighteen age and body mass index-matched healthy controls were also included.
INTERVENTION: Hypothyroid individuals were treated with levothyroxine according to European Thyroid Association guidelines.
MAIN OUTCOMES: Changes in hunger sensation were assessed using visual analog scales (cm) before and during a standardized mixed meal test, and food intake was measured during a subsequent ad libitum meal (g).
RESULTS: After six months of levothyroxine therapy, mean resting energy expenditure was increased by 144 kcal/day (10%) (P < 0.001). Weight loss was comprised of 0.8 kg fat-free mass while fat mass remained unchanged. Fasting hunger sensation increased from a mean of 4.5 (SD 2.2) cm to 5.5 (SD 2.2) cm (P = 0.047). The numerical increase in ad libitum meal intake did not reach statistical significance.
CONCLUSION: Our data suggest that levothyroxine-induced hunger may be a culprit in the lack of fat mass loss from levothyroxine therapy.
PMID:37582332 | DOI:10.1530/EC-23-0314
