Endocrine Glands Endocrine Glands Hypothalamus Pituitary Anterior lobe

Endocrine Glands

Endocrine Glands • Hypothalamus • Pituitary – Anterior lobe – Posterior lobe • Thyroid gland • Parathyroid glands • Adrenal Glands – Cortex – Medulla Hormonal Communication • Islets of Langerhans • Gonads – Ovaries – Testes • Pineal gland • Thymus • others

Hypothalamus • Part of brain – Regulates ANS, emotions, feeding/satiety, thirst, body temperature, etc. – Hormones related to these functions • “Releasing hormones” • Axonal transport to posterior lobe

Anterior Pituitary • “Releasing” hormones regulate AP aka adeno hypo physis “glands” “under” “growth” • All proteins – TSH (thryoid stimulating hormone/thyrotropin) – ACTH (adrenocorticotropic hormone) – FSH (gonadotropin) – LH (gonadotropin) • Tropins/tropic hormones – GH (growth hormone) – Prolactin-releasing H Hypothalamic Pituitary Axis Animation : IP Web

Anterior Pituitary

Anterior P. Homeostatic Imbalances Growth hormone (GH or h. GH) – Promotes mitosis, cell division – Elongation of long bones, etc. – Healing of wounds Lack of h. GH retards growth – Hypersecretion in youth produces giantism – Hyposecretion in childhood produces pituitary dwarfism – Hypersecretion in adult produces acromegaly

Posterior Pituitary • Axonal transport to Posterior Pituitary aka neuro hypo physis “nerve” “under” “growth” • Hypothalamic cell bodies synthesize – oxytocin – ADH

Pituitary—Posterior lobe • Oxytocin – Stimulates smooth muscle contraction of uterus & mammary glands. • Antidiuretic H. – Stimulates water reabsorption in collecting ducts. – Stimulates vasoconstriction (vasopressin) – Lack diabetes insipidus

Posterior Pituitary Homeostatic Imbalances ADH – Hyposecretion produces diabetes insipidus “tasteless” – Excessive thirst and urination • central or neurogenic DI • gestagenic or gestational DI • nephrogenic DI • dipsogenic DI Diabetes Insipidus Foundation, Inc.

Thyroid Gland • Location in neck – Inferior to larynx – Anterior & lateral to trachea • Composed of follicles – Follicle cells produce thyroglobulin • Thyroxin (T 4) • Triiodothyronine (T 3) – Both “thyroid hormone”, body’s major metabolic hormone • Parafollicular/ C cells • Calcitonin – Decreases blood Ca 2+ by depositing it in bones

Homeostatic imbalances • Hypothyroidism results – Myxedema (in adults) – Goiter—low levels of iodine – Cretinism (in children) • Hyperthyroidism results – Graves disease

Parathyroid Glands • Four small glands embedded in posterior of thyroid – Parathyroid hormone (PTH) – Stimulates osteoclasts to free Ca 2+ from bone – Stimulates Ca 2+ uptake from intestine & kindey Hormonal Regulation of Calcium

Parathyroid Homeostatic Imbalances • Severe hyperparathyroidism causes massive bone destruction • If blood Ca 2+ fall too low, neurons become overactive, resulting in tetany

Feedback Loop • Negative feedback in calcium homeostasis. A rise in blood Ca 2+ causes release of calcitonin from the thyroid gland, promoting Ca 2+ deposition in bone and reducing reabsorption in kidneys. • A drop in blood Ca 2+ causes the parathyroid gland to produce parathyroid hormone (PTH), stimulating the release of Ca 2+ from bone. • PTH also promotes reabsorption of Ca 2+ in kidneys and uptake of Ca 2+ in intestines.

Adrenal Glands One on top of each kidney • Cortex – Corticosteroid – glandular • Medulla – Catecholamines – neurohormonal • Epinephrine • Norepinephrine

Adrenal Cortex • Cortex – Activity stimulated by ACTH – Controls prolonged responses by secreting corticosteroids. – Mineralcorticoids • Aldosterone regulate salt and water balance – Glucocorticoids • Cortisol regulate glucose metabolism and the immune system. – Gonadocorticoids • Androgens • Estrogens

Adrenal Cortex Imbalances • Hypersecretion leads to Cushing’s disease – ACTH-releasing tumors or side effects of corticoid drugs. • Hyposecretion leads to Addison’s Disease – Deficits in glucocorticoids and mineralcorticoids

Adrenal Medulla • Medulla – The adrenal medulla mediates short–term responses by secreting catecholamine hormones. – Cells are modified neurons (lack axons) • Epinephrine (adrenaline) • Norepinephrine (noreadrenaline) – enable a rapid ( fight-or-flight ) responses to stress by increasing blood glucose and blood pressure and directing blood to the heart, brain, and skeletal muscles.

Pancreas • Consists of two major types of secretory tissues which reflects its dual function – Exocrine gland • secretes digestive juice • localized in the acinar cells – Endocrine gland • releases hormones • localized in the islet cells (islets of Langerhans)

Pancreatic Islets • “About a million” embedded in pancreas • Control centers for blood glucose – Insulin from beta cells – Glucagon from alpha cells

Insulin Glucagon

Islets of Langerhans • Insulin stimulates glucose uptake, glycogenesis • Glucagon stimulates glycogenolysis, glucose release from liver (vs gluconeogenesis)

Feedback Loop • A rise in blood glucose causes release of insulin from beta cells the pancreas, promoting glucose uptake in cells and storage as glycogen in the liver. • A fall in blood glucose stimulates alpha cells in the pancreas to secrete glucagon, which causes the liver to break down glycogen and release glucose.

Pancreas Homeostatic Imbalances Diabetes “siphon” mellitus mel= “honey” Symptoms: • Polyuria • Polydipsia • Polyphagia Blood Level Regulation in Diabetics

Gonads • Ovaries – Estrogens – Progesterone • Testes – Testosterone • Reproductive functions when we study reproductive system.

Pineal gland • Melatonin – ? Inhibits early puberty – ? Day/night cycles • Timing of sleep, body temperature, appetite • Secretes melatonin during darkness – Participates in setting the body’s clock • Melatonin is a potent antioxidant • Melatonin is high when young and is reduced as we age

Thymus • Thymus gland • Thymopoietins, thymic factor, thymosins – Influence development of T lymphocytes

Non-Endocrine Gland Hormones • Stomach (gastrin) • Small intestine (duodenum intesetinal gastrin, secretin, cholecystokinin) • Heart (atrial natriuretic peptide) • Kidneys (erythropoietin, active vitamin D 3) • Adipose tissue (leptid, resistin) • Skin • Placenta (human chorionic gonadotropin, human placental lactogen, relaxin)

Functions regulated by the Endocrine System • • Growth Healing Water balance & Blood Pressure Calcium Metabolism Energy Metabolism Stress Regulation of other Endocrine Organs

Growth • Growth hormone-releasing hormone • Human growth hormone (h. GH) • Thyrotropin (TSH) • Thyroxine & triiodothyronine • Calcitonin • Somatostatin (GHIH)

Healing • Growth hormone-releasing hormone • Human growth hormone (h. GH) • Thyrotropin (TSH) • Thyroxine & triiodothyronine • Calcitonin • Glucagon, Insulin • Erythropoietin

Water balance & Blood pressure • • • ADH Aldosterone Angiotensin II Atrial natriuretic H. Epinephrine

Calcium Metabolism • • Calcitonin Parathyroid H. (PTH) Estrogens/androgens Growth hormone

Energy Metabolism • Thyroxine & triiodothyronine • Thyroid-stimulating H. (thyrotropin, TSH) • Epinephrine & norepinephrine • Insulin • Glucagon • Adrenocorticotropic H. (ACTH) • Cortisol

Stress • • Epinephrine & norepinephrine T 4 &T 3 ? ? ACTH Cortisol