Endocrine Glands

Endocrine Glands• Hypothalamus• Pituitary

– Anterior lobe– Posterior lobe

• Thyroid gland• Parathyroid

glands• Adrenal Glands

– Cortex– Medulla

• Islets of Langerhans

• Gonads– Ovaries– Testes

• Pineal gland• Thymus• others

Hormonal Communication

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 hGH)– Promotes mitosis, cell division– Elongation of long bones, etc.– Healing of wounds Lack of hGH

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 akaneuro 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 (T4)• Triiodothyronine (T3)

– Both “thyroid hormone”, body’s major metabolic hormone

• Parafollicular/ C cells• Calcitonin

– Decreases blood Ca2+ 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 Ca2+ from bone– Stimulates Ca2+ uptake

from intestine & kindey

Hormonal Regulation of Calcium

Parathyroid Homeostatic Imbalances

• Severe hyperparathyroidism causes massive bone destruction

• If blood Ca2+ fall too low, neurons become overactive, resulting in tetany

Feedback Loop• Negative feedback in

calcium homeostasis. A rise in blood Ca2+ causes release of calcitonin from the thyroid gland, promoting Ca2+ deposition in bone and reducing reabsorption in kidneys.

• A drop in blood Ca2+ causes the parathyroid gland to produce parathyroid hormone (PTH), stimulating the release of Ca2+ from bone.

• PTH also promotes reabsorption of Ca2+ in kidneys and uptake of Ca2+ 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 ImbalancesDiabetes “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 (duodenumintesetinal

gastrin, secretin, cholecystokinin)• Heart (atrial natriuretic peptide)• Kidneys (erythropoietin, active vitamin D3)• 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 (hGH)• Thyrotropin (TSH)• Thyroxine & triiodothyronine• Calcitonin • Somatostatin (GHIH)

Healing

• Growth hormone-releasing hormone

• Human growth hormone (hGH)• 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

• T4 &T3 ??

• ACTH• Cortisol