Evaluation of Dynapenia in Patients with Subclinical Hypothyroidism

Abstract Background Dynapenia is defined as a decline in muscle strength without a corresponding loss of muscle mass, representing a condition different from sarcopenia. Hypothyroidism can negatively affect musculoskeletal function; similarly, subclinical hypothyroidism, although generally asymptomatic, may have almost the same effects. This study aimed to evaluate muscle strength in individuals with subclinical hypothyroidism and to investigate the relationship between subclinical hypothyroidism and dynapenia. Materials and Methods In this cross-sectional study, 172 participants were included—86 patients diagnosed with subclinical hypothyroidism and 86 euthyroid controls—who were admitted to the Internal Medicine Outpatient Clinic of University of Health Sciences Umraniye Training and Research Hospital between February and June 2024. Thyroid function tests (TSH and fT4) were recorded, muscle strength was assessed using a hand dynamometer, and muscle mass was evaluated using bioelectrical impedance analysis. Muscle strength values and the prevalence of dynapenia were compared between the two groups. Statistical analyses were performed using independent t-test, Mann–Whitney U test, and chi-square test as appropriate. Results The mean age of the participants was 42.3 ± 11.3 years, with a similar sex distribution between groups (female: 79%, male: 21% each group). The mean BMI was 26.3 ± 3.4 kg/m 2 . The subclinical hypothyroidism group had higher TSH levels (6.0 ± 1.1 vs. 2.3 ± 0.9 mIU/L) and lower fT4 levels (1.1 ± 0.1 vs. 1.3 ± 0.2 ng/dL) compared to controls (p < 0.001). Mean handgrip strength was significantly lower in the subclinical hypothyroidism group (19.5 ± 5.6 kg vs. 24.5 ± 4.8 kg) (p < 0.001). The prevalence of dynapenia was 82.7% in the subclinical hypothyroidism group and 17.3% in the control group (p < 0.001). Conclusion Subclinical hypothyroidism is significantly associated with the development of dynapenia. This association may be related to the regulatory effects of thyroid hormones on muscle metabolism and muscle fiber synthesis.