Principles of Biochemistry

9.1.4.4 Hormones secreted by Thyroid

9.1.4.4 Hormone secreted by Thyroid

The thyroid gland secretes two hormones thyroxine and L–tri iodothyronine.These two hormones, abbreviated T₄ and T₃, respectively, are derivatives of tyrosine.

The thyroid hormones are carried by the blood to their targets. Most tissues are stimulated by the thyroid hormones. They increase intestinal glucose absorption, glycogenolysis in liver and muscle and promote gluconeogenesis. They increase RNA, amino acid transport and protein synthesis. They are essential for the conversion of β carotene to vitamin A.

Hypothyroidism causes cretinism in children and Myxoedema in adults. Hyperthyroidism leads to toxic goiter.