hormones of anterior pitutaty

hypothalmic factors and hormones of anterior pitutary and its applied

1. Hypothalamic factors and Anterior Pituitary Hormones By Abdul Majid Siddiqui MSc. Medical Physiology

2. Learning Objectives To understand the structure and function of anterior pituitary To understand the different hormones secreted by anterior pituitary To understand the control of hypothalamus over anterior pituitary Applied aspect of anterior pituitary

3. Hormone of Anterior Pituitary. The pituitary gland also called the hypophysis , is a small gland—about 1 cm in diameter and 0.5 to 1 gm in weight—that lies in the sella turcica , a bony cavity at the base of the brain, and is connected to the hypothalamus by the pituitary stalk. Physiologically, the pituitary gland is divisible into two distinct portions: Anterior pituitary. P osterior pituitary.

4. Anterior pituitary gland contains several different cell types that synthesize and secrete hormones.

5. Six important peptide hormones plus several less important ones are secreted by the anterior pituitary. The hormones of the anterior pituitary play major roles in the control of metabolic functions throughout the body, 1. Growth hormone promotes growth of the entire body by affecting protein formation, cell multiplication, and cell differentiation. 2. Adrenocorticotropin ( corticotropin ) controls the secretion of some of the adrenocortical hormones, which affect the metabolism of glucose, proteins, and fats. 3. T hyroid-stimulating hormone (TSH) controls the rate of secretion of thyroxine and triiodothyronine by the thyroid gland, and these hormones control the rates of most intracellular chemical reactions in the body. 4. Prolactin promotes mammary gland development and milk production. Two separate gonadotropic hormones:- 5. F ollicle-stimulating Hormone(FSH) 6. Luteinizing Hormone(LH), They control growth of the ovaries and testes, as well as their hormonal and reproductive activities.

6. Metabolic functions of the anterior pituitary hormones.

7. Physiological Functions of Growth Hormone All the major anterior pituitary hormones, except for growth hormone, exert their principal effects by stimulating target glands, including thyroid gland, adrenal cortex, ovaries, testicles, and mammary glands. Effect on Growth It causes growth of almost all tissues of the body Promotes increase in the size of cells. Increase the rate of mitosis, resulting in increase number of cells. Causes differentiation of cells in bone and muscle.

8. Effect on Bone and Cartilage Growth hormone stimulate bone growth. Increase the number of cells responsible for bone growth. Increase deposition of protein by chondrocytic & osteogenic Causes growth of epiphysial cartilage. Delays fusion of epiphysial with the shaft. Effects on Protein metabolism. It increase the rate of protein synthesis in the cells by Enhancing amino acid transport through the cell membrane. Increases nuclear transcription of DNA to form mRNA. Enhancing RNA translation to prone protein synthesis by ribosome. Decreasing the catabolism of protein and amino acids. Effects on Carbohydrate metabolism. Decrease the use of glucose for energy; Diminishes uptake of glucose by the cells and increase blood glucose conc. Increase the secretion of insulin.

9. Effect on fat metabolism Increase mobilization of fats from adipose tissue. Increase free fatty acids in the blood. Enhances use of fatty acids for energy. Excess of growth hormone has a “ Ketogenic effect.” Effect On Electrolyte Metabolism Causes rise in plasma phosphorous and fall in blood urea, N 2 and amino acid level. Increases GI absorption of Ca ++ . Reduces Na + and K + excretion. Growth hormone is degraded in the Liver and Kidneys.

10. „ OTHER HORMONES OF ANTERIOR PITUITARY Thyroid-stimulating Hormone (TSH) TSH is necessary for the growth and secretory activity of the thyroid gland. It has many actions on the thyroid gland. Adrenocorticotropic Hormone (ACTH) ACTH is necessary for the structural integrity and the secretory activity of adrenal cortex. Follicle-stimulating Hormone (FSH) Follicle-stimulating hormone is a glycoprotein made up of one α-subunit and a β-subunit. The α-subunit has 89 amino acids and β-subunit has 112 amino acids. The half-life of FSH is about 3 to 4 hours.

11. Follicle Stimulating Hormones(FSH) In males, FSH acts along with testosterone and accelerates the process of spermeogenesis In females FSH: Causes the development of graafian follicle from primordial follicle Stimulates the theca cells of graafian follicle and causes secretion of estrogen Luteinizing Hormone (LH) In males, LH is also known as interstitial cell-stimulating hormone (ICSH) because it stimulates the interstitial cells of Leydig in testes. This hormone is essential for the secretion of testosterone from Leydig cells. In females FSH: Causes ovulation and formation of Corpus Luteum in ovary

12. Prolactin Prolactin is a single chain polypeptide with 199 amino acids. Its half-life is about 20 minutes. Prolactin is necessary for the final preparation of mammary glands for the production and secretion of milk. Prolactin acts directly on the epithelial cells of mammary glands and causes localized alveolar hyperplasia.

13. Hypothalamus Controls Pituitary Secretion:- Almost all secretion by the pituitary is controlled by either hormonal or nervous signals from the hypothalamus Secretion by the anterior pituitary is controlled by hormones called hypothalamic releasing and hypothalamic inhibitory hormones (or factors) secreted within the hypothalamus itself and then conducted to the anterior pituitary through minute blood vessels called hypothalamic- hypophysial portal vessels . In the anterior pituitary, these releasing and inhibitory hormones act on the glandular cells to control their secretion. Hypothalamic- hypophysial portal system

14. Hypothalamic Releasing and Inhibitory Hormones That Control Secretion of the Anterior Pituitary Gland Hormone Structure Primary Action on Anterior Pituitary Thyrotropin -releasing hormone (TRH) Peptide of 3 amino acids Stimulates secretion of TSH by thyrotropes Gonadotropin -releasing hormone ( GnRH ) Single chain of 10 amino Stimulates secretion of FSH and LH by gonadotropes Corticotropin -releasing hormone (CRH) Single chain of 41 amino acids Stimulates secretion of ACTH by corticotropes Growth hormone–releasing hormone(GHRH) Single chain of 44 amino acids Stimulates secretion of growth hormone by somatotropes Growth hormone inhibitory hormone ( somatostatin ) Single chain of 14 amino acids Inhibits secretion of growth hormone by somatotropes Prolactin -inhibiting hormone (PIH) Dopamine (a catecholamine) Inhibits secretion of prolactin by lactotropes

15. APPLIED PHYSIOLOGY – DISORDERS OF ANTERIOR PITUITARY GLAND HYPERACTIVITY OF ANTERIOR PITUITARY 1. Gigantism 2. Acromegaly Normal hand; B. Acromegalic hand

16. HYPOACTIVITY OF ANTERIOR PITUITARY 1. Dwarfism Dwarfism is a pituitary disorder in children, characterized by the stunted growth. Causes Reduction in GH secretion in infancy or early childhood causes dwarfism. Chandra Bahadur Dangi Height-55 cm Jyoti-Amge Height- 64 cm