Chapter 20 The Endocrine Glands Endocrine Functions and

Chapter 20 The Endocrine Glands

Endocrine Functions and Dysfunctions • Endocrine glands release hormones directly into the blood to regulate various metabolic functions • The major endocrine glands – Pituitary – Thyroid – Parathyroid – Adrenal cortex and medulla – Pancreatic islets – Ovaries and testes

Endocrine Functions and Dysfunctions • Feedback mechanisms – The amount of hormone synthesized and released by a gland may be regulated: • Directly: • Indirectly: – Negative feedback systems are most commonly used • An increase in hormone or hormone-regulated substance leads to:

Pituitary Gland • Suspended by stalk from hypothalamus at base of brain – Composed of: • Anterior lobe: – Growth hormone: – Prolactin: – Thyroid-stimulating hormone (TSH): – Adrenocorticotrophic hormone (ACTH): – Follicle-stimulating hormone (FSH): – Luteinizing hormone (LH): • Posterior lobe: – Antidiuretic hormone (ADH): – Oxytocin:

Pituitary Gland

Normal mechanisms controlling elaboration of tropic hormones by the pituitary gland

Pituitary Hypofunction • Panhypopituitarism is a condition in which the: – Leads to impaired function of: • Pituitary dwarfism is a condition that occurs when a child has a deficiency of: – Causes:

Pituitary Hypofunction • Diabetes insipidus is a disease caused by failure of the: – Can be caused by: – Unable to absorb: – Causes excretion of: – Person will compensate by:

Pituitary Tumors • Many pituitary endocrine disturbances caused by anterior lobe pituitary tumors – Functional tumors: • Clinical manifestations depend on: – Nonfunctional tumors: • May encroach on important surrounding structures – Treatment determined by type, size, and hormone produced by tumor • Drugs to suppress tumor growth • Surgical resection: usual surgical approach is through the nasal cavity

Pituitary Tumors • Growth hormone overproduction caused by a tumor – Causes excessive growth in length of bones at growth plate (epiphyses) in children which is called: • The effected person will become too tall – Causes thickening of bones and enlargement of viscera in adults which is called: • Does not alter height since epiphyses are closed • Prolactin overproduction caused by a tumor – Causes: • galactorrhea: • Amenorrhea:

Acromegaly Gigantism Fig. 20 -3

Thyroid Gland • Found in the neck overlying the upper section of trachea • Consists of two lateral lobes connected by a narrow isthmus • Composed of thyroid follicles that produce and store thyroid hormone – Hormone production regulated by: • Actions – Controls rate of: – Required for normal:

Thyroid Gland

Normal thyroid gland, illustrating two lateral lobes connected by narrow isthmus Fig. 20 -4

Thyroid Gland • Hyperthyroidism: • Hypothyroidism: Hyperthyroidism Hypothyroidism Rapid pulse Slow pulse Increased metabolism Decreased metabolism Hyperactive reflexes Sluggish reflexes Emotional Placid GI effect: diarrhea GI effect: constipation Warm, moist skin Cold, dry skin

Nontoxic Goiter • Thyroid gland enlarges to increase hormone secretion – Caused by inadequate secretion of: • 3 major factors predispose – Iodine deficiency » Iron is needed to: – Enzyme deficiency or impaired enzyme function » Enzyme is needed to: – Increased hormone requirements • Treatment: administer thyroid hormone; may need surgical removal

The pathogenesis of nontoxic goiter Fig. 20 -5

Toxic Goiter/Hyperthyroidism • Excess secretion of: – Usually caused by an autoimmune disease in which autoantibodies target cells of the: • Autoantibodies bind to TSH receptors and cause: • Normal control mechanisms are lost • This condition is also called: • Treatment – Antithyroid drugs, thyroidectomy, large doses of radioactive iodine

Toxic Goiter goiter Fig. 20 -7 Large nodular Fig. 20 -6

Hypothyroidism • In adult – Individuals have low levels of: – Causes slowing of: – Treatment: & high levels • In an infant – May be caused by: • Failure of the thyroid gland to: • Deficiency of enzymes needed for: – If left untreated will cause perm stunting of growth and mental retardation which is called: • All newborn infants are screened • Early diagnosis and treatment required for normal development

Chronic Thyroiditis • Preferably referred to as: • Immune system develops autoantibodies that destroy: • Results in hypothyroidism • Cant stop disease progression of disease but can give thyroid hormone

Parathyroid Glands • Blood calcium levels are in equilibrium with calcium in bones – Adequate blood calcium levels are needed for normal cardiac & skeletal muscle contraction, nerve impulse transmission, & blood clotting • Parathyroid hormone regulates calcium levels by: – Regulating the release of calcium from: – Absorption of calcium in the: – Excretion of calcium by the:

Hyperparathyroidism • Increased levels of parathyroid hormone • Usually from a hormone-secreting parathyroid tumor • Increased output of hormone causes: – Hypercalcemia: – Excessive calcium is withdrawn from: • Bones become: – Excessive calcium excreted in urine – Treatment:

Hypoparathyroidism • Decreased levels of parathyroid hormone • Usually from accidental removal of parathyroid glands during thyroid surgery • Decreased output of hormone causes: – Hypocalcemia: – Leads to neuromuscular: • Treatment: raise calcium levels – High-calcium diet – Supplementary vitamin D

Adrenal Gland • Adrenals: paired glands above kidneys • Consists of an inner medulla and outer cortex – Each region secretes different hormones

Adrenal Cortex • Secretes 3 major classes of hormones – Glucocorticoids • Raise blood glucose by – Promoting glucose utilization in tissues – Promoting fat and protein breakdown • Suppress inflammation • Major hormone is: – Mineralocorticoids • Regulate electrolyte & water balance by promoting absorption of sodium & water, & excretion of potassium in the kidneys • Major hormone is: – Sex hormones • Produce small amounts of estrogen & testosterone in males and females

Addison Disease • Addison Disease occurs with: – Results from: • Most cases are caused by an: – Glucocorticoid (cortisol) deficiency results in: – Mineralocorticoid deficiency results in an inability to regulate: • Sodium concentration of the blood falls as well as: – Treat by administering deficient hormones

Cushing Disease and Syndrome • Cushing Disease and Syndrome – Glucocorticoid excess causes: • Blood glucose: • Protein synthesis is impaired & proteins are: – Leads to: • Fat accumulates on trunk & extremities appear: • Skin becomes thin and easily: • Face appears full & round which is referred to as: – Mineralocorticoid excess leads to increase in:

Cushing’s disease before treatment. Fig. 20 -12

Adrenal Medulla • Produces catecholamines that stimulate the sympathetic nervous system – Norepinephrine (noradrenaline) – Epinephrine (adrenaline) • Pheochromocytoma is a tumor that secretes large amounts of: – Produces high blood pressure (hypertension) & increased heart rate – May cause cerebral hemorrhage from: – Symptoms may come and go or may be continuous – Treatment:

Pancreatic Islets • Diabetes Mellitus was discussed in Chapter 16

Gonads • Two functions – Production of germ cells – Production of sex hormones: controlled by gonadotropic hormones of pituitary gland FSH and LH • Tumors may secrete hormones • Treatment: surgical excision

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