chapter 13- endocrinology

Endocrinology

The medical specialty that studies the anatomy and physiology of the endocrine system and treats endocrine system diseases

Hyperpituitarism

General term for hyper secretion of one or more hormones from the anterior pituitary gland. \n • Caused by presence of an adenoma. \n • Treatment is drug therapy to suppress hormone secretion or surgery to remove the adenoma followed by radiation therapy

Hypopituitarism

General term for hyposecretion of one or more hormones from the anterior pituitary gland. \n • Caused by injury or defect in the anterior pituitary gland. \n • Treatment is drug therapy to replace the deficient hormones

Hypothalamus

As an endocrine gland: \n –It secretes hormones that stimulate or inhibit the secretion of other hormones from the anterior pituitary gland. \n –It produces A D H (antidiuretic hormone) and oxytocin and \n triggers their secretion from the posterior pituitary gland.

Galactorrhea

Hypersecretion of prolactin due to an adenoma in the anterior pituitary gland; results in production of milk even though the patient is not pregnant or nursing

Failure of lactation

Hyposecretion of prolactin due to a defect in the anterior pituitary gland; prevents development of the milk glands during puberty and results in inability to breastfeed

Gigantism

Condition in which hypersecretion of growth hormone during childhood and puberty causes excessive growth of bones and tissues

Acromegaly

Condition in which hypersecretion of growth hormone during adulthood causes a person’s facial features, jaw, hands, and feet to widen and enlarge

Dwarfism

Condition in which hyposecretion of growth hormone during childhood and puberty causes a lack of growth and short stature, but with normal body proportions.

Syndrome of inappropriate antidiuretic hormone (SIADH)

Condition in which hypersecretion of antidiuretic hormone (ADH) causes the kidneys to increase reabsorption of excessive amounts of water and some sodium. \n • Reabsorption dilutes the blood and causes a low blood sodium level. \n • Low blood sodium leads to headache, weakness, confusion, and coma

Diabetes insipidus (DI)

Condition in which hyposecretion of ADH causes the kidneys to decrease reabsorption of sodium and water. \n • Decreased reabsorption results in polyuria. \n • Water loss from polyuria leads to weakness and polydipsia

Uterine inertia

Condition in which hyposecretion of oxytocin causes weak and uncoordinated uterine contractions during childbirth. \n • Results in prolonged labor and delayed birth. \n • Postpartum hemorrhage may occur because the uterus does not contract properly

Seasonal affective disorder (SAD)

Condition in which decreased hours of sunlight during fall and winter lead to hypersecretion of melatonin accompanied by a decrease in serotonin levels. \n • Symptoms include depression, decreased energy, and weight gain. \n • Treatment involves phototherapy and possible drug therapy with antidepressant medication

Hyperthyroidism

Condition in which the thyroid gland secretes too much T3 and T4. \n • Symptoms include tremors, tachycardia, palpitations, restlessness, nervousness, diarrhea, insomnia, fatigue, weight loss, exophthalmos, goiter, dry eyes, and slow eyelid closing. \n • Treatment involves antithyroid drugs and/or thyroidectomy followed by radiation therapy or administration of radioactive iodine

Graves’ Disease

Edema behind the eyeballs causes them to protrude. This creates a staring expression that shows a large amount of white sclerae

Goiter

\
Chronic, progressive enlargement of the thyroid gland; also known as thyromegaly. \n • Goiters can also be caused by thyroid cancer, chronic inflammation of the thyroid gland, or lack of iodine. \n • Adenomatous goiters or nodular goiters are caused by (usually benign) growths in the thyroid gland. \n • When there is too little iodine in the diet, the thyroid gland enlarges to help it capture more iodine; the result is known as a simple goiter, nontoxic goiter, or endemic goiter.

Hypothyroidism

\
Condition in which the thyroid gland secretes too little T3 and T4. \n • Usually caused by iodine deficiency. \n • May also result from a congenital defect or Hashimoto thyroiditis (an autoimmune disorder in which the body makes anti-thyroid antibodies). \n • Symptoms include fatigue, low body temperature, dry hair and skin, constipation, and weight gain. \n • Severe cases involve myxedema (swelling), tingling in hands and feet, lack of menstruation, hair loss, enlarged heart and tongue, slow speech, and mental impairment.

Thyroid carcinoma

Cancerous or malignant tumor of the thyroid gland. \n • Causes enlargement of the thyroid gland with hoarseness and neck pain. \n • Usually slow growing and has a high cure rate

Hyperparathyroidism

Condition in which hypersecretion of parathyroid hormone moves too much calcium from the bones into the blood. \n • Movement of calcium causes hypercalcemia and bone fragility. \n • Other symptoms include muscle weakness, fatigue, depression, and kidney stones

hypoparathyroidism

Condition in which hyposecretion of parathyroid hormone leads to hypocalcemia. \n • Usually caused by accidental removal of the parathyroid glands during thyroidectomy. \n • Symptoms include nerve irritability, skeletal muscle cramps, and spasms

Glucagon

secreted by alpha cells to stimulate glycogen breakdown when blood glucose is low

Insulin

secreted by beta cells to move glucose from the blood into cells

somatostatin

\
secreted by delta cells to inhibit secretion of glucagon, insulin, and growth hormone

Hyperinsulinism

Condition in which a pancreatic adenoma causes hypersecretion of insulin. \n • High insulin levels lead to low blood glucose (hypoglycemia). \n • Symptoms of hypoglycemia include shakiness, headache, sweating, dizziness, and fainting. \n • If untreated, hypoglycemia can progress to insulin shock and coma.

Insulin resistance syndrome (IRS)

Condition in which hypersecretion of insulin occurs because cell receptors develop resistance to insulin. \n • Receptor resistance means glucose remains in the blood instead of entering body cells. \n • The pancreas senses the high glucose level and tries to lower it by secreting more insulin. \n • Eventually, the pancreas becomes exhausted and the patient develops diabetes mellitus

Diabetes Mellitus (DM)

Condition in which the beta cells of the pancreas are unable to secrete enough insulin. \n • Low insulin levels result in elevated blood glucose (hyperglycemia) \n • Glycosuria (excess glucose in the urine) occurs as the kidneys work to rid the body of the excess glucose. \n • Polyuria (production of large amounts of urine) then develops as the glucose brings water along with it. \n • Excessive urination leads to polydipsia \n • Inability to metabolize glucose leads to polyphagia

Type 1 DM

\
Also called insulin-dependent diabetes mellitus (IDDM) because the pancreas secretes no insulin and the patient must receive insulin injections. \n • Sometimes known as juvenile-onset diabetes mellitus because it develops during childhood, adolescence, or young adulthood. \n • Is an autoimmune disease in which the body makes antibodies against the islets of Langerhans. \n • Requires exogenous insulin (shots or insulin pump)

Type 1.5 DM

Also called latent autoimmune diabetes in adults (LADA). \n • Similar to type 1 diabetes mellitus in that it is an autoimmune disorder in which the body makes antibodies against the pancreas. \n • The pancreas still secretes some insulin—just not enough.

Type 2 DM

Also called non-insulin-dependent diabetes mellitus (NIDDM) or adult-onset diabetes mellitus (AODM). \n • Is not the result of an autoimmune disorder. \n • Instead, insulin secretion is decreased because the patient is obese and has developed insulin resistance

Gestational diabetes mellitus (GDM)

Occurs in some women during pregnancy, when increased levels of estradiol and progesterone block the action of insulin; resolves upon delivery of the baby

Diabetic ketoacidosis (DKA)

Condition in which a high level of acidic substances called ketones accumulates in the blood because the body metabolizes fat rather than glucose; this lowers the blood pH and can lead to diabetic coma

Diabetic neuropathy

Decreased or abnormal sensation in the extremities due to damage to the myelin sheaths around nerves

Diabetic nephropathy

Condition in which high levels of glucose and ketones cause degenerative changes in the nephrons of the kidneys; can lead to kidney failure

Diabetic retinopathy

Degenerative changes in the retina due to the local effect of excess glucose and ketones; also involves formation of fragile blood vessels that rupture easily

Atherosclerosis

Formation of fatty deposits and plaques in the arteries; process is accelerated in patients with DM because of abnormalities in fat metabolism

Impotence

Difficulty achieving an erection; may occur as a result of nerve damage and atherosclerosis

Foot injury

Patients with DM are at increased risk due to poor eyesight and decreased sensation. \n • Wound healing is slow because of poor blood flow and high blood glucose. \n • Small injuries may progress to ulcers or gangrene

Adrenal cortex secretes these hormones:

when stimulated by ACTH (adrenocorticotropic hormone):

\- Mineralocorticoids \n –Glucocorticoids \n –Androgens

norepinephrine

increases heart rate, blood pressure, and blood glucose

epinephrine (adrenaline)

raises blood pressure and prepares for the “fight-or-flight” response

dopamine

released during times of stress

Hyperaldosteronism

Condition in which hypersecretion of aldosterone causes reabsorption of large amounts of sodium and water from the kidneys into the blood; this results in hypertension, electrolyte imbalance, and weakness

Hypoaldosteronism

Condition in which hyposecretion of aldosterone causes a low level of sodium in the blood; this results in dizziness, weakness, and decreased blood pressure.

Cushing syndrome

Condition in which hypersecretion of cortisol stimulates the liver to convert too much glycogen to glucose; this elevates \n blood glucose levels and results in rapid weight gain. \n • Fat deposits develop in the abdomen, face, and upper back. \n • Thinning of connective tissue causes red cheeks and abdominal striae. \n • Decreased protein synthesis leads to muscle wasting and weakness

Addison disease

Condition in which hyposecretion of cortisol leads to low blood glucose, fatigue, weight loss, and decreased ability to tolerate stress, disease, or surgery; the skin also develops an unusual bronzed color

Adrenogenital syndrome (also known as congenital adrenal hyperplasia (CAH)

Condition in which hypersecretion of androgens causes alterations in sexual characteristics. \n • In girls, the clitoris and labia enlarge to resemble a penis and scrotum. \n • In boys, precocious puberty occurs. \n • In adult females, hypersecretion leads to virilism, amenorrhea, and excessive dark hair on the forearms and face (hirsutism)

Pheochromocytoma

Condition in which hypersecretion of epinephrine and norepinephrine causes heart palpitations, severe sweating, headaches, and severe hypertension that can lead to stroke; caused by an adrenal adenoma with a gray-tan appearance

Precocious puberty F

Early onset of puberty due to hypersecretion of estradiol; characterized by premature development of the breasts and female secondary sexual characteristics, as well as early onset of menstruation and ovulation

Menopause

Cessation of menstruation due to hyposecretion of estradiol in an adult female. \n • Is a normal result of the aging process but can also be caused by removal of the ovaries. \n • Accompanied by vaginal dryness, thinning of the hair, lack of sexual drive, and hot flashes.

Precocious puberty M

Early onset of puberty due to hypersecretion of testosterone; involves premature development of male secondary sexual characteristics, growth of facial hair, deepening of the voice, and sperm production

Gynecomastia

Enlargement of the breasts due to hyposecretion of testosterone in an adult male

Calcium test

Test that measures the level of calcium in the blood; can reveal whether the parathyroid gland is secreting a normal amount of parathyroid hormone

Cortisol level test

Test that measures the amount of cortisol in the blood to determine if the adrenal cortex is working; also indirectly determines whether the anterior pituitary gland is secreting ACTH to stimulate the adrenal cortex

Fasting blood sugar (FBS)

Test that measures the blood glucose level after a patient has fasted for at least 12 hours. \n • Results indicate whether the pancreas is secreting a normal amount of insulin. \n • Also called a fasting plasma glucose (FPG) or fasting blood glucose (FBG) test. \n • Is the initial screening test for diabetes mellitus

Glucose self-testing

Procedure in which patients measure their own blood glucose level one or more times each day to ensure it is maintained within normal range.

Oral glucose tolerance test (OGTT)

Test in which a blood specimen is drawn after the patient fasts for 12 hours, then once every hour for 4 hours after the patient consumes a glucose drink. \n • Usually, blood glucose is elevated at first but returns to a normal level in 1 to2 hours. \n • A continuing elevated blood glucose indicates diabetes mellitus

Hemoglobin A1c (HbA1c) test

Test that measures the A1c fraction of hemoglobin in a diabetic patient’s red blood cells; higher levels indicate poor blood glucose control during the past several months.

FSH assay and LH assay

Test that measures levels of follicle-stimulating hormone and luteinizing hormone. \n • Results indicate whether the anterior pituitary gland is secreting normal amounts of these hormones. \n • Included in male and female infertility workups

Growth Hormone test

Test that measures the level of growth hormone in the blood to determine whether the anterior pituitary gland is secreting a normal amount

Testosterone test

Test that measures levels of total testosterone and free testosterone in a man’s blood to determine if the testes are secreting a normal amount. \n • Also indirectly determines if the anterior pituitary gland is secreting enough luteinizing hormone. \n • Done as part of an infertility workup.

Thyroid function tests TFTs

\
Test that measures blood levels of T3, T4, and TSH. \n • T3 and T4 levels reveal whether the thyroid is functioning correctly. \n • TSH level reveals whether the anterior pituitary gland is functioning correctly. \n • Values from these tests can be used to calculate the patient’s free thyroxine index

ADH stimulation test

Test that measures urine concentration to determine if the posterior pituitary gland is secreting a normal amount of antidiuretic hormone (ADH). \n • Patient provides a urine specimen after not drinking for 12 hours, then receives ADH and water and provides a second urine specimen. \n • If the patient has diabetes insipidus (DI), the second specimen will be more concentrated.

Estradiol test

Test that measures the level of estradiol in a woman’s urine to determine if the ovaries are secreting normal amounts of this hormone. \n • Also indirectly evaluates whether the anterior pituitary gland is secreting adequate FSH (Done as part of an infertility workup)

Urine dipstick test

Test that measures glucose, ketones, and other substances in the urine; used to evaluate patients with diabetes mellitus

Vanillylmandelic acid (VMA) test

Test that measures levels of VMA, a byproduct of epinephrine and norepinephrine. \n • Requires a 24-hour urine sample. \n • Results help reveal whether the adrenal medulla is functioning correctly

Radioactive iodine uptake (RAIU) and thyroid scan

Test that combines a thyroid scan and a nuclear medicine procedure. \n • Thyroid scan shows the size and shape of the thyroid gland. \n • Radioactive iodine uptake shows how well the thyroid gland absorbs iodine from the blood. \n • A normal scan shows uniform distribution of radioactive iodine throughout the thyroid gland

Thyroid ultrasonography

Procedure that uses sound waves to produce an image of the thyroid gland; can show enlargement and/or presence of nodules.

ADA diet

Physician-prescribed diet for patients with diabetes mellitus (DM) that follows guidelines established by the American Diabetes Association (ADA). Carbohydrate and fat intake are limited

Antidiabetic drugs

Oral medications used to treat type 2 diabetes mellitus. \n • Act by stimulating the pancreas to secrete more insulin or by increasing the number of insulin receptors on cells. \n • Cannot be used to treat type 1 diabetes mellitus

Antithyroid drugs

Used to treat hyperthyroidism by inhibiting production of T3 and T4; alternative treatment is to administer radioactive sodium iodine 131 to destroy thyroid cells

Thyroid hormone supplement drugs

Drugs that treat a lack of thyroid hormones and hypothyroidism

Corticosteroids

Drugs that mimic the action of cortisol from the adrenal cortex; hormone therapy for Addison disease.

Growth hormone supplement drugs

Drugs that provide growth hormones to people who are deficient

Insulin

Used to treat type 1 and type 1.5 diabetes mellitus, as well as type 2 diabetes mellitus that can’t be controlled with oral antidiabetic agents. \n • Must be injected at least once per day to control blood glucose levels. \n • Different types of insulin are classified by speed and duration of action. \n • Closed loop systems (pumps + continuous glucose monitors (CGMs)) Drugs

Treatments for diabetes

type 1- requires drug therapy with insulin

type 2- typically managed with oral anti-diabetic drugs and occasionally insulin

type 1.5- treated similarly to type 2, although insulin will more likely be required

Adrenalectomy

Procedure to remove the adrenal gland because of an adenoma or cancerous tumor.

Fine-needle biopsy

Procedure that uses a fine needle to take a small sample of tissue from a thyroid nodule to determine whether the nodule is benign or cancerous

Parathyroidectomy

Procedure to remove one or more of the parathyroid glands to treat hyperparathyroidism; may also occur accidentally during thyroid surgery

Thymectomy

Procedure to remove the thymus in patients with myasthenia gravis

Thyroidectomy

Procedure to remove all or part of the thyroid gland

Transsphenoidal hypophysectomy

Procedure to remove an adenoma from the pituitary gland by way of an incision in the sphenoid sinus.

ACTH

adrenocorticotropic hormone

ADA

American Diabetes Association/American Dietetic Association

ADH

antidiuretic hormone

AODM

adult-onset diabetes mellitus

CDE

certified diabetes educator

CGM

continuous glucose monitoring

DI

diabetes insipidus

DKA

diabetic ketoacidosis

DM

diabetes mellitus

FBG

fasting blood glucose

FBS

fasting blood sugar

FSH

follicle-stimulating hormone

FTI

free thyroxine index

GDM

gestational diabetes mellitus

GH

growth hormone

GTT

glucose tolerance test

HBA1c

hemoglobin A1c

IDDM

insulin-dependent diabetes mellitus

IRS

insulin resistance syndrome