The hypothalamic-pituitary-thyroid axis (HPT axis) is a neuroendocrine system that regulates metabolism.  When the hypothalamus senses low circulating levels of the hormones T3 and T4, it signals to the pituitary, which then signals the thyroid gland to release T3 and T4.  T4 normally is converted to the more active T3, but T4 can also be converted … Continue reading Melatonin Suppresses Thyroid Hormones