Hormones What is Hormones Hormones are the chemical

Hormones

What is Hormones - Hormones are the chemical messengers of the body. They are defined as organic substances secreted into blood stream to control the metabolic and biological activities. -These hormones are involved in transmission of information from one tissue to another and from cell to cell. -These substances are produced in small amounts by various endocrine (ductless) glands in the body.

- They are delivered directly to the blood in minute quantities and are carried by the blood to various target organs where these exert physiological effect and control metabolic activities. -Thus frequently their site of action is away from their origin. Hormones are required in trace amounts and are highly specific in their functions. -The deficiency of any hormones leads to a particular disease, which can be cured by administration of that hormone.

Functions of the hormones Reproduction and sexual differentiation Development and growth Homeostasis Regulation of metabolism Regulation of nutrient supply

Endocrine hormone molecules are secreted (released) directly into the bloodstream, whereas exocrine hormones (or ectohormones) are secreted directly into a duct, and, from the duct, they flow either into the bloodstream or from cell to cell by diffusion in a process known as paracrine signalling.

A paracrine mechanism is defined as chemical communication between neighboring cells within a tissue or organ. Autocrine signals are those in which a chemical acts on the same cell - Intracrine signal is generated by a chemical acting within the same cell.

Endocrine glands

Classification of Hormones Chemical composition Solubility Hydrophopic Hydrophilic Mechanism of action Intracellular receptors Cell surface receptors

Classification of Hormones

Mechanism of hormones action Group I Hormones binds to intracellular receptors. Steroids, T 3, T 4 Group II Hormones binds to cell surface receptors. Amino acid derivatives, glycoprotein

Secreted hormone Growth Hormone Thyroid stimulating hormone (thyrotropin) Abbreviation Effect GH Stimulates growth and cell reproduction TSH Stimulates thyroxine (T 4) and triiodothyronine (T 3) synthesis and release from thyroid gland Stimulates iodine absorption by thyroid gland

Adrenocorticotrophic hormones Follicle stimulating hormone ACTH Stimulates corticosteroid (glucocorticoid and mineralcorticoid) androgen synthesis and release from adrenocortical cells FSH In females: Stimulates maturation of ovarian follicles in ovary In males: Stimulates maturation of seminiferous tubules In males: Stimulates spermatogenesis

Triiodothyronine Thyroxine Calcitonine T 3 T 4 Stimulates body oxygen and energy consumption, increasing the basal metabolic rate Stimulates RNA polymerase promoting protein synthesis Stimulates body oxygen and energy consumption, thereby increasing the basal metabolic rate Stimulates RNA polymerase I and II, thereby promoting protein synthesis Stimulates osteoblasts and thus bone construction Inhibits Ca 2+ release from bone, thereby reducing blood Ca 2+