Resting Energy Expenditure in Obese Women with Primary Hypothyroidism and Appropriate Levothyroxine Replacement Therapy

Abstract

Context Growing evidence suggests that appropriate levothyroxine (LT4) replacement therapy may not correct the full set of metabolic defects afflicting individuals with hypothyroidism. Objective To assess whether obese subjects with primary hypothyroidism are characterized by alterations of the resting energy expenditure (REE). Design Retrospective analysis of a set of data about obese women attending the outpatients service of a single obesity center from January 2013 to July 2019. Patients A total of 649 nondiabetic women with body mass index (BMI) > 30 kg/m2 and thyrotropin (TSH) level 0.4–4.0 mU/L were segregated into 2 groups: patients with primary hypothyroidism taking LT4 therapy (n = 85) and patients with normal thyroid function (n = 564). Main outcomes REE and body composition assessed using indirect calorimetry and bioimpedance. Results REE was reduced in women with hypothyroidism in LT4 therapy when compared with controls (28.59 ± 3.26 vs 29.91 ± 3.59 kcal/kg fat-free mass (FFM)/day), including when adjusted for age, BMI, body composition, and level of physical activity (P = 0.008). This metabolic difference was attenuated only when adjustment for homeostatic model assessment of insulin resistance (HOMA-IR) was performed. Conclusions This study demonstrated that obese hypothyroid women in LT4 therapy, with normal serum TSH level compared with euthyroid controls, are characterized by reduced REE, in line with the hypothesis that standard LT4 replacement therapy may not fully correct metabolic alterations related to hypothyroidism. We are not able to exclude that this feature may be influenced by the modulation of insulin sensitivity at the liver site, induced by LT4 oral administration.

Evaluation of Thyroid Hormone Replacement Dosing in Morbidly Obese Hypothyroid Patients after Bariatric Surgery-Induced Weight Loss

“…Another aspect to be considered is that hypothyroid treated patients could have metabolic differences with euthyroid subjects. Muraca et al have found that obese hypothyroid patients in LT4 therapy, with a normal serum TSH level when compared with euthyroid subjects, are characterized by reduced resting energy expenditure, which is in accordance with the hypothesis that THR may not completely correct metabolic disturbances due to hypothyroidism [53]. Mele et al [54] have found that compared with euthyroid obese patients, LT4 users presented higher adiposity.…”

Hypercortisolism and altered glucose homeostasis in obese patients in the pre‐bariatric surgery assessment

“…Indirect calorimetry was performed continuously, while lying quietly, after an overnight fast in a comfortable and thermoregulated room, for 30 minutes during the basal equilibration period with a ventilated hood system (Sensor Medics 2900; Metabolic Measurement Cart) in order to measure VO 2 and VCO 2 to calculate energy expenditure. The mean coefficient of variation (CV) values within the session for both O 2 and CO 2 measurements were below 2% 22 …”

“…Anthropometric features were assessed using a balance with stadiometer (SECA 711). Body composition was assessed as previously described 22 by BIA using a leg‐to‐leg TANITA SC‐240 MA Body Composition Analyzer (TANITA, Japan). Patients were asked to stand on the Body Composition Analyzer with bare feet and to remove all the accessories containing metal.…”

Thyroid Function Alteration in Obesity and the Effect of Bariatric Surgery

“…Decreased thyroid function treated patients could be metabolically different when compared with normal subjects. Accordingly, it has been found that obese hypothyroid women on levothyroxine therapy, with normal circulating thyrotropin values, have a diminished energy expenditure, suggesting that standard levothyroxine replacement does not fully correct metabolic alterations related to hypothyroidism [ 101 ]. Furthermore, other studies have encountered that hypothyroid patients treated with levothyroxine showed higher adiposity and similar insulin resistance, but healthier lipid levels compared with euthyroid obese patients [ 102 ].…”