Endocrine System Lecture Notes PDF

Endocrine glands Presented by D/Suzan Moustafa Hazzaa Professor of medical physiology Menoufia university  Pituitary gland Site: hypophyseal fossa (sella turcica). Shape: 1 2 Connections between hypoth...

Endocrine glands Presented by D/Suzan Moustafa Hazzaa Professor of medical physiology Menoufia university  Pituitary gland Site: hypophyseal fossa (sella turcica). Shape: 1 2 Connections between hypothalamus and pituitary 1 - hypothalamo-hypophyseal portal circulation. 2- hypothalamo-hypophyseal portal tract. With anterior pituitary (adenohypophysis) 1- hypothalamo-hypophyseal portal circulation: through it, the hypothalamus can regulate anterior pituitary secretions by releasing and inhibitory factors. With posterior pituitary (neurohypophysis) 2- hypothalamo-hypophyseal portal tract: through it, ADH and oxytocin which are synthesized in the hypothalamus are transported to the posterior pituitary.  Anterior Pituitary (adenohypophysis) Hormones secreted by anterior pituitary Hormones with direct metabolic functions: 1. Growth hormone (GH). 2. Prolactin. Hormones with trophic functions: 1. Thyroid stimulating hormone (TSH). 2. Adrenocorticotrophic hormone (ACTH). 3. Gonadotrophic hormones (GTH) and it includes luteinizing hormone (LH) and follicle stimulating hormone (FSH). Control of anterior Pituitary secretions 1- hypothalamic control: 5 4 3 2 1 Growth h. releasing h Growth h. inhibitory h. 2- Feedback control: Growth hormone Effect on growth: Effect on metabolism: Functions of growth Hormone: A-Effect on growth 1- Effect on bone growth: ✓ Increase proliferation of epiphyseal cartilage. ✓ Increase Ca++ uptake …….. calcification of cartilage. ✓ Increase mineralization of bone. 2- Effect on soft tissue growth: ✓ Increase growth of Skeletal muscle. ✓ Increase growth of all organs. B-Effect on metabolism 1- Effect on carbohydrate metabolism: hyperglycemic and diabetogenic ✓ decrease glucose uptake and utilization. ✓ Increase gluconeogenesis. ✓ Increase glycogenolysis in the liver. 2- Effect on protein metabolism : protein anabolic ✓ Increase amino acid uptake by cells. ✓ Increase transcription and translation ………… increase protein synthesis. 3- Effect on lipid metabolism: lipolytic and ketogenic ✓ Increase lipolysis ………….. Increase plasma FFA (lipemia). ✓ Increase FFA oxidation in the liver…….. Keton bodies (ketonemia). 4- Effect on electrolyte metabolism : ✓ Increase Ca++ absorption from GIT. ✓ decrease excretion of Na+, K+ and HPO4 + +.  Control secretion of growth Hormone: 1- hypothalamic control: ❑ GHRH. ❑ GHRIH (somatostatin). 2- Feedback control: ❑ -ve short loop by GH on hypothalamus (GHRH). 3- other factors affecting GH: Factors increasing GH: ❑ blood glucose FFA. ❑ Proteins in diet. ❑ Fasting. ❑ Exercise and stress. Factors decreasing GH: ❑ blood glucose FFA. ❑ Proteins in diet. ❑ Obesity. ❑ Exogenous GH.  Abnormal GH secretion Diseases related to abnormal growth hormone Decreased Oversecretion secretion Before After puberty puberty Pituitary dwarfism Giantism Acromegally  Pituitary Dwarfism It is a syndrome due to decreased growth hormone secretion before union of epiphysis. Causes: - decreased GH secretion from anterior pituitary. Manifestations: 1- symmetrical skeletal growth retardation. *proportionate * short stature 2- soft tissue growth retardation. 3- Normal mentality and sexuality. 4- Facial features (Childish face with small lips & nose) also, the face of the child will often look much younger than other’s in his age group (Doll Face).  Gigantism It is a syndrome due to over secretion of growth hormone before union of epiphysis. Causes: - adenoma of cells secreting GH in the anterior pituitary. Manifestations: 1- symmetrical overgrowth of long bones. *proportionate * long stature 2- soft tissue overgrowth. 3- Hypogonadism. 4- pituitary diabetes (insulin insensitive).  Acromegaly It is a syndrome due to over secretion of growth hormone after union of epiphysis. Causes: - adenoma of cells secreting GH in the anterior pituitary. Manifestations: 1- increased thickness of short bones (hands and feet). 2- Overgrowth of all soft tissues and visceromegaly. 3- Kyphosis due to enlargement of the vertebrae. 4- Facial features (big skull - depressed and enlarged nose forward protrusion of enlarged mandible). 5- Pituitary diabetes (insulin insensitive).  Prolactin Hormone It is secreted from anterior pituitary gland. Functions of prolactin hormone: In female: 1- It Stimulates milk formation (lactogenesis) and secretion: during lactation ✓ It is secreted within 2-3 days after labour. ✓ It stimulates mammary glands to synthesize casein, fat and lactose. 2- It can inhibit ovulation in lactating woman: ✓ It inhibits GTH of pituitary or GnRH of the hypothalamus. ✓ So it inhibits ovulation and menstruation (amenorrhea). In male: 1- Stimulates development of cells in the testis in the pre-pubertal period. 2- It is involved in the development of the prostate and seminal vesicle.  Posterior Pituitary (Neurohypophysis) Hormones stored by posterior pituitary 1. Antidiuretic hormone (ADH). 2. Oxytocin.  Antidiuretic hormone (Vasopressin) is synthesized mainly in nuclei of the hypothalamus. Functions of ADH hormone: 1- Effect on the kidney: ✓ It acts on V2 receptors on basal border of cells in the DCT of the kidney. ADH increases water reabsorption → water retention in the body → production of concentrated urine. 2- Effect on blood vessels: ✓ On physiological dose …………….. It has no effect on B.V. ✓ On pharmacological dose …………… it acts on V1A receptors on B.V. ………….. direct vasoconstriction of all B.V. 3- Effect on smooth muscles of the uterus and small intestine: ✓ It has a direct action on the smooth muscles of the uterus and small intestine (like oxytocin). Regulation of secretion of ADH 1- Changes in the ECF (extra cellular fluid) volume: ✓ Decreased ECF volume ……… stimulate hypothalamus to secrete ADH. 2- Changes in the ABP: ✓ Decreased ABP ……. stimulate hypothalamus to secrete ADH. 3- changes in the ECF osmolarity: ✓ Increase the osmolarity > 300 m osmol/l ………. Dehydration which stimulates osmo-receptors in the hypothalamus and increase ADH secretion. 3- other factors affecting ADH: Factors increasing ADH: ❑ Hot weather. ❑ Nicotin, morphine. Factors decreasing ADH : ❑ Cold weather. ❑ Opiate. ❑ Ethyl alcohol.  Hyposecretion of ADH (Diabetes insipidus) It occurs due to decreased ADH secretion. Causes: 1- Distruction of the hypothalamic nuclei or their axons. 2- failure of the kidney to respond to ADH. Manifestations: 1- Polyurea. 2- polydepsia. 3- loss of water soluble vitamins due to polyurea. 4- increase the BMR.  Oxytocin is synthesized mainly in nuclei of the hypothalamus. similar to ADH. Functions of oxytocin hormone: 1- In female: ✓ Uterine contraction in pregnant female during labour: it stimulates the contraction of the uterus directly. after labour: it stimulates the involution of the uterus which helps in the descent of the placenta and prevent postpartum he. ✓ Milk ejection during lactation by contraction of myoepithelial cells.  Control secretion of oxytocin hormone: 1- Unconditioned reflexes: ❑ During suckling. ❑ During labour. 2- Conditioned reflexes: ❑ Seeing or hearing the baby ……oxytocin secretion and milk ejection. Prolactin / oxytocin and lactation Thank you 32