Abstract

Background: Thyroid hormones are essential regulators of energy expenditure, thermogenesis, and body composition. Although overt thyroid dysfunction is well known to alter basal metabolic rate (BMR) and body mass, emerging evidence suggests that even hormonal variations within the reference range may exert measurable effects on metabolic and body composition profiles. Women of reproductive age represent a population particularly sensitive to hormonal oscillations due to the interplay between endocrine, reproductive, and cardiometabolic health. Objective: The study aimed to a) analyze thyroid hormone levels (TSH, FT3, FT4) alongside anthropometric and body composition parameters in women of reproductive age; b) examine thyroid hormone levels, BMR, and body composition parameters across age groups; and c) investigate associations of thyroid hormones with BMR, body composition components, and unfavorable body composition patterns (visceral adiposity, elevated metabolic age, obesity) as well as metabolic indicators.. Methods: A total of 117 women aged 18–45 years were included in this cross-sectional, observational study conducted in Bosnia and Herzegovina between September 2023 and November 2024. Thyroid hormone levels were measured using electrochemiluminescence assays, while body composition was assessed by bioelectrical impedance analysis. Statistical analyses included descriptive methods, Pearson’s correlation, and Chi-square testing, with significance set at p

Key words: Thyroid Hormones, Body Composition, Obesity.