Thyroid Hormones



Thyroid hormones, which include T3 and T4, are hormones produced by the thyroid gland. The production pathway of these hormones happens in several steps. First, thyroid-releasing hormone, or TRH, is released from the hypothalamus. TRH then stimulates the anterior pituitary to release thyroid-stimulating hormone or TSH, the second step in the pathway. Finally, TSH acts on the thyroid gland to promote release of the thyroid hormones T3 and T4.

Key Points

  • Thyroid Hormones
    • T3 = Triiodothyronine
    • T4 = Thyroxine
    • Origin: Thyroid
    • Pathway:
      • TRH from hypothalamus
      • TSH from anterior pituitary
      • Thyroid Hormones
    • Type: Tyrosine derivatives
      • Steroid-like
    • Trigger: TSH stimulation from anterior pituitary
    • Target: Whole body
      • Effect: Increases metabolic rate
        • Metabolic rate is often measured as the amount of energy of energy expended in one day