Does Metformin Therapy Affect Thyroid Function Tests in Euthyroid Obese
Adolescents?
Abstract
Background Metformin has been frequently used off-label for childhood
obesity besides diabetes. Studies have demonstrated the
thyroid-stimulating hormone (TSH) suppressive effect of metformin in
patients with a diagnosis of primary hypothyroidism. This study aimed to
evaluate free T4 (fT4) and free T3 (fT3) tests and influencing factors
in adolescents (TSH) who were on metformin therapy for obesity and
insulin resistance and had no diagnosed thyroid disease. Material and
Methods A total of 54 patients aged 10-18 years who presented to the
Pediatric Endocrinology Outpatient Clinic for overweight between 2017
and 2020 and who were diagnosed with exogenous obesity and insulin
resistance based on examinations by excluding hypothyroidism were
retrospectively evaluated. Baseline and post-treatment 6-month thyroid
function tests, HOMA-IR, and anthropometric measurements were evaluated.
Results Of the 54 patients included in the study, 38 (70.4%) were
female and 16 (29.6%) were male. the mean time from admission to
follow-up was 6.5±2.7 months. There was a moderate negative (inverse)
correlation between the change in weight SDS (∆weight SDS) and the
change in fT4 (∆fT4) of the patients (r=-0.319), and a moderate positive
correlation between ∆weight SDS and the change in fT3 value (∆fT3)
(r=0.534) (p=0.035; p=0.027, respectively). A moderate significant
positive correlation was found between the change in HOMA-IR (∆HOMA-IR)
and the change in TSH (∆TSH) (r=0.376; p=0.009).