Drug Name: Levo-T (levothyroxine sodium)
Company: Mova Pharmaceutical
Approval Status: Approved March 2002
Treatment for: Hypothyroidism

General Information
Levo-T (levothyroxine sodium) has been approved by the FDA for the treatment of hypothyroidism and the suppression of thyroid stimulating hormone. Levo-T will be available in dosages ranging from 25 mcg to 300 mcg.

Mechanism of Action
Synthetic levothyroxine (T₄) is identical to that produced naturally in the human thyroid gland. Thyroid hormone synthesis and secretion is regulated by the hypothalamic-pituitarythyroid axis. Thyrotropin-releasing hormone (TRH) released from the hypothalamus stimulates secretion of thyroid-stimulating hormone, TSH, from the anterior pituitary. TSH, in turn, is the physiologic stimulus for the synthesis and secretion of thyroid hormones, L-thyroxine (T₄) and L-triiodothyronine (T₃), by the thyroid gland. Circulating serum T₃ and T₄ levels exert a feedback effect on both TRH and TSH secretion. When serum T₃ and T₄ levels increase, TRH and TSH secretion decrease. When thyroid hormone levels decrease, TRH and TSH secretion increase.