 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. There is transcription, translation, and post-translational modifications. The hormones in the first step are produced as large proteins, 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 lumen of endoplasmic reticulum and as a result they are converted into pro-hormones. These 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 are they remain bound with the plasma membrane and they are released when they are required. The release of peptide hormone occurs by exocytosis. Dear students, 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. This way they are not kept in secretive vesicles but when the stimulus is received, it is instantly made from cholesterol and released. For this purpose, cell maintains 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. Diffusion is easy because they are lipid soluble molecules so they can diffuse out by simple diffusion. Dear students, 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 quite common to them but after synthesis, there is a little difference in their packaging. After synthesizing the thyroid hormones, a protein called thyroglobulin is bind with it. And by binding, they are stored in the thyride follicles whereas catecholamines, i.e. epinephrine and norepinephrine, after making them in the adenyl medulla, they are stored in vesicles and a protein which is called chromogranine protein is bind with it. In this way, 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.