Major Endocrine Organs

Pituitary Gland

Secretes: Growth Hormone (GH), Thyroid-Stimulating Hormone (TSH), Adrenocorticotropic Hormone (ACTH), Follicle-Stimulating Hormone (FSH), Luteinizing Hormone (LH), Prolactin (PRL), Antidiuretic Hormone (ADH), and Oxytocin

Anterior Pituitary

Manufactures and Releases Six Hormones: 4 Tropic Hormones (Thyroid-Stimulating Hormone (TSH), Adrenocorticotropic Hormone (ACTH), Gonadotropins (Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH)

2 Non-Tropic Hormones: Prolactin (PRL) and Growth Hormone (GH)

Thyroid-Stimulating Hormone (TSH)

Function: Stimulates normal development and secretory activity of the thyroid gland

Adrenocorticotropic Hormone (ACTH)

Function: Stimulates the adrenal cortex to release corticosteroid hormones

Gonadotropins (FSH and LH)

produced by the hypothalamus

Follicle-Stimulating Hormone (FSH)

In both sexes: stimulates gamete (sperm and egg) production and maturation

In females: stimulates estrogen secretion, responsible for the growth and development of egg-containing follicles in the ovaries, and causes the egg to grow; matures the egg

In males: causes the maturation of the sperm

Leutinizing Hormone (LH)

In both sexes: promotes the production of gonadal hormones (sex hormones)

In females: acts with FSH to cause the maturation of an egg-containing ovarian follicle; by itself, it triggers ovulation and promotes synthesis and release of ovarian hormones (estrogen and progesterone)

In males: stimulates the interstitial cells of the testes to produce testosterone; aka, interstitial cell-stimulating hormone (ICSH) in males

-Feed back to suppress FSH and LH release

Prolactin (PRL)

In females: promotes breast development and stimulates milk production; prolactin levels rise and fall with estrogen blood levels; high levels of estrogen - PRH and PRL release; Low levels of estrogen - PIH release; rise in PRL just before menses causes breast swelling and tenderness in some women; in pregnant women, sustained PRH release is stimulated by infant sucking

In males: enhances testosterone secretion in males

Growth Hormone (GH)

Function: stimulates body cells to increase in size, esp. muscle and bone cells; accelerates the rate of mitosis (increases cell division)
-Important in the growth and development of children: stimulation of the epiphyseal plate = long bone growth; stimulation of skeletal muscle = increase in muscle mass

-concentrations decrease with age

Hypersecretion of GH

In children = gigantism

In adults = acromegaly

Hyposecretion of GH

In children = pituitary dwarfism

In adults = not usually a problem; but in rare instances, progeria = rapid aging

Posterior Pituitary

DOES NOT MANUFACTURE ANY HORMONES; releases 2 hormones produced in the hypothalamus: antidiuretic hormone (ADH) and oxytocin

Oxytocin

Function: stimulates contraction of smooth muscles in the uterus during labor and causes ‘let down’ and release of breast milk

Antidiuretic Hormone (ADH)

Function: prevents wide swings in water balance by helping the body avoid dehydration and water overload

Hypersecretion of ADH

Can be seen: in children with meningitis, following neurosurgery, following hypothalamic injury, ectopic ADH secretion by cancer cells (esp. pulmonary cancers), and following general anesthesia or administration of certain drugs

-Syndrome of inappropriate ADH secretion (SIADH): fluid retention, headache, disorientation due to brain edema, weight gain, hypo-osmolarity of the blood

Hyposecretion of ADH

Diabetes insipidus: insufficient amounts of ADH, output of copious amounts of urine and intense thirst, can be caused by physical damage to the hypothalamus or posterior pituitary

Thyroid Hormone (TH)

Stimulates enzymes involved in glucose oxidation, enhances protein synthesis and lipid breakdown, maintains blood pressure, regulates tissue growth and development, critical for normal skeletal and nervous system growth and development and reproductive capabilities

Hypersecretion of TH

Grave’s Disease: elevated metabolic rate, sweating, rapid, irregular heartbeat, nervousness, weight loss despite adequate food intake, and exophthalmos (protrusion of the eyeballs)

Hyposecretion of TH

In infants = cretinism (reversible with early detection, developmental abnormalities are irreversible)

In adults = myxedema

Calcitonin

Lowers blood Ca+ concentration levels; produced by the parafollicular cells (or C cells); directly antagonistic to parathyroid hormone; targets the skeleton

Parathyroid Hormone (PTH)

raise blood calcium levels; produced by chief cells

Hypersecretion of PTH

Rare; usually results from parathyroid gland tumor

Hyposecretion of PTH

results from parathyroid gland trauma or removal during thyroid surgery; can also be caused by an extended deficiency of dietary magnesium (functional parathyroidism)

Cortisol

inhibits the synthesis of proteins, promotes the release of fatty acids (used to make energy), stimulates gluconeogenesis (the production of new glucose from non-carbohydrate sources), regulated by negative feedback

Hypersecretion of Cortisol

Cushing’s Disease

-Hyperglycemia, loss of muscle and bone protein; increased water in the blood and tissues > hypertension and edema

Hyposecretion of Cortisol

Addison’s Disease = caused by insufficient production of glucocorticoids and mineralocorticoids

-Weight loss, hypertension, dehydration, low glucose and sodium levels in the blood, bronze skin

Alpha Cells

Secrete Glucagon

-Increases blood sugar levels when they get low: stimulates gluconeogenesis in the liver, promotes breakdown of glycogen, causes glucose release by the liver, and is inhibited by somatostatin

Beta Cells

Secrete Insulin

-Decreases blood glucose levels when they get high: promotes the movement of glucose through the cell membranes, stimulates the storage of both glucose and fats, stimulates glycogen and protein synthesis

Delta Cells

Secrete Somatostatin

-Secreted in response to the rise in blood glucose, fatty acids, and amino acids after a meal, acts as a hormone and a paracrine, inhibits the secretion of glucagon and insulin by the neighboring alpha and beta cells, the reason for function under speculation

Type I

Juvenile onset diabetes = insufficient insulin production

Type II

Adult onset diabetes = insulin does not affect the cells of the body

Kindeys

Produce: erythropoietin (RBC production)

Heart

Produce: Atrial natriuretic protein (response to high blood pressure)

Placenta

Produce: pregnancy hormones

GI

Mucosa

Skin

Produce: Cholecalciferol (Inactive vitamin D)