Biotin-(L-Thyroxine) is a biotinylated L-Thyroxine, a synthetic hormone used in hypothyroidism research. DIO enzymes convert this compound (T4) into the biologically active thyroid hormone, Triiodothyronine (T3) [1].

Deiodinases (DIO) that catalyze the conversion of thyroxine (prohormone) to active thyroid hormone are related to thyroid-stimulating hormone (TSH) levels. DIO1 and DIO2 facilitate the activation of thyroid hormone secretion, while DIO3 contributes to hormone inactivation. DIO1 and DIO2 are crucial in the negative feedback regulation of pituitary TSH secretion [1]. Biotin-(L-Thyroxine) (T4) and triiodothyronine (T3) hormones are known to regulate ion channels, pumps, and contractile proteins. Thyroid hormones influence calcium homeostasis and the fluxes responsible for excitation and contraction, with Biotin-(L-Thyroxine) and triiodothyronine modulating their pharmacological control and secretion. In rats fed an iodine-deficient diet for 12 weeks, levels of triiodothyronine and Biotin-(L-Thyroxine) were significantly reduced compared to those on a standard diet (p<0.001). In groups treated with low-dose Biotin-(L-Thyroxine), Biotin-(L-Thyroxine) levels increased (p=0.02), while triiodothyronine levels remained similar to controls (p=0.19). Rats treated with high-dose Biotin-(L-Thyroxine) showed significantly increased circulating triiodothyronine and Biotin-(L-Thyroxine) concentrations compared to the untreated hypothyroid group (p<0.001 and p=0.004, respectively), with Biotin-(L-Thyroxine) levels also significantly elevated compared to control values (p=0.03) [2].