Liothyronine and Levothyroxine Facilitates Fat, Weight Loss in Older Adults With Subclinical Hypothyroidism

Liothyronine (LT3) is associated with greater loss of fat mass and weight than levothyroxine (LT4) in older adults with subclinical hypothyroidism, according to study results presented at ENDO 2021, held virtually from March 20 to 23, 2021.

Subclinical hypothyroidism is common among older adults, but the physiological effects of liothyronine and levothyroxine in this population are not well known.

In this study, researchers evaluated the physiological effects of liothyronine and levothyroxine in 13 adults aged 70 years and older with persistent subclinical hypothyroidism. Outcome measures included vital signs, weight and body composition, thyroid symptoms, cognitive function, resting energy expenditure, lipids, bone mineral content, bone density, and quality of life.

Results revealed that compared with baseline (mean TSH=4.84 [1.29] μIU/mL), participants on LT3 and LT4 had an average weight loss of 2.5 kg (P <.001) and 1.1 kg (P <.02). Participants on LT3 experienced a decrease in fat mass by an average of 1.5 kg (P <.01 vs baseline) while those on LT4 experienced a decrease of 0.7 kg (P =.03 vs baseline). Other significant differences were observed between LT3 and LT4 in total cholesterol and low-density lipoprotein cholesterol, both of which produced lower numbers on LT3 compared with LT4.

Researchers concluded that liothyronine led to greater decreases in fat mass and weight after each treatment and that liothyronine and levothyroxine produce different physiologic responses among older adults with subclinical hypothyroidism.

Reference

Meizlik P, Cucchiara A, Kannan L, et al. Physiologic effects of levothyroxine and liothyronine in the in older individuals with persistent subclinical hypothyroidism: a randomized, double-blind, cross-over study. Presented at: ENDO 2021; March 20-23, 2021. Presentation OR20.