 Dear students, in this topic we shall discuss the mechanism of synthesis of hormones. First we shall discuss the synthesis of peptide and protein hormones. Peptide and protein hormones are synthesized on the rough endoplasmic reticulum of endocrine cells. It follows the mechanism of protein synthesis in the cell, the hormones in the first step are produced as large proteins and as such it is comparatively larger in size and has extra amino acids with it and this hormone is called pre-pro hormone. It is a direct result of translation of the transcripted messenger RNA. This pre-pro hormone is not the active form of hormone. These pre-pro hormones are sent into the endoplasmic reticulum. These pre-pro hormones are then transferred to the Golgi bodies where they are packaged into secretive granules. Inside the secretive granules there are certain enzymes which further cleave them and produce smaller active hormones out of them. These vesicles with active hormone are stored within the cytoplasm R. They remain bound with the plasma membrane and they are released when they are required. The release of peptide hormone occurs by exocytosis. Now we shall discuss the synthesis of steroid hormones. The steroid hormones are not stored in the glandular cells. They are synthesized from cholesterol instantly when the stimulus is received. These cells maintain a large store of cholesterol which can be rapidly utilized. Steroid hormones are also not packaged in the vesicles. Once they are synthesized, they are immediately diffused out of the cell and enter the blood. Their diffusion is easy because they are lipid soluble molecules. They can diffuse out by simple diffusion. Now we shall discuss the synthesis of amine hormones. The amine hormones which are produced from the thyroid and adenyl medulla are synthesized by the action of enzymes on amino acid tyrosine. The method of synthesis of tyrosine is very common but there is a difference in packaging. After synthesizing thyroid hormones, a protein called thyroglobulin is binded with it. Thyroglobulin is binded with it and stored in the polycols of the thyroid. Catecholamines, i.e. epinephrine and non-epinephrine are binded with the adenyl medulla. Both types of hormones are bound with proteins in the vesicles. However, before secretion, they are cleaved from their respective proteins. Thyroid amines are split from the thyroglobulin and the freed hormones are released into the blood. When they enter the blood, these thyroid hormones, when they enter the blood, they again combine with plasma proteins which slowly release them in their target tissues. Similarly, catecholamines are released from chromogranines before their exocytosis from adenyl medullary cells. When these catecholamines enter the blood, they can exist in the plasma in free form or they bind with the other substances.