Endocrine System Disorders

• The lecture notes cover disorders of the endocrine system, focusing on the pituitary, thyroid, calcium movement, adrenals, and endocrine pancreas.
• The notes describe the key aspects of endocrine function, pathophysiology of select conditions, signs and symptoms, diagnostic tests, and basic treatment modalities.

Endocrine System General Information

• The endocrine system relies on negative feedback: high hormone levels suppress secretion, while low levels stimulate it.
• Endocrine disorders typically involve hyposecretion or hypersecretion.

Pituitary Gland Disorders

• The pituitary gland, or hypophysis, is the master gland that secretes hormones that govern other glands.
• The pituitary secretes antidiuretic hormone (ADH), thyroid-stimulating hormone (TSH), and adrenocorticotropic hormone (ACTH).

Diabetes Insipidus (DI)

• DI is caused by undersecretion of ADH, leading to excessive dilute urine production.
• In DI, diabetes means "to pass too much urine," and insipidus means "flavorless."
• Renal-related etiology involves "sick" kidneys with decreased response of renal tubules to ADH.
• Central nervous system etiologies include pituitary tumors that diminish ADH secretion.
• CNS: Head injuries and cerebral edema can cause diminished ADH release.
• Without ADH, water flows from capillaries into tubules becoming dilute urine.
• Polyuria of dilute urine leads to thirst; drinking water leads to more urination.
• Low water in the blood compartment causes concentration to increase, causing serum osmolality to increase.
• High blood osmolality causes water to be pulled out of tissues, dehydrating and shrinking the tissue cells.
• Signs and symptoms of dehydration include poor skin turgor and dry mucous membranes.

Syndrome of Inappropriate Antidiuretic Hormone (SIADH)

• SIADH is caused by oversecretion of ADH.
• SIADH is triggered by ectopic ADH production from small-cell bronchogenic cancer.
• It is also caused by drugs affecting the brain, specifically general anesthetics.
• Trauma to the brain, tumors, or head injury can also cause SIADH.
• High ADH levels cause the body to hold onto too much water, decreasing urination.
• Increased vascular fluid volume dilutes the plasma compartment, leading to lower serum osmolality and small amounts of highly concentrated urine.
• Signs and symptoms include decreased urine output (oliguria) and fluid overload, leading to edema.

Thyroid Gland Disorders

• Thyroid gland function is regulated by TSH from the pituitary.
• TSH stimulates the thyroid to produce and store thyroxine (T4) and triiodothyronine (T3).
• T3/T4 hormones regulate body metabolism and calcitonin increases calcium movement from the blood into the bone.
• Adequate T3 and T4 production depends on iodide uptake from the blood, which comes from dietary sources such as seafood and iodized salt.
• T3 and T4 act on cells and affect metabolic rate, caloric requirements, oxygen consumption, carbohydrate & lipid metabolism, growth & development, and brain & nervous system functions.
• Reduced T3 and T4 levels causes the pituitary to secrete TSH, stimulating the thyroid, and re-establishing T3 and T4 levels and suppress TSH.
• Increased T3 and T4 levels causes the opposite effect.

Hyperthyroidism

• Hyperthyroidism is a state of excess T3 and T4 production and release.
• The most common cause of hyperthyroidism is Graves disease, an autoimmune disorder.
• In Graves disease, autoantibodies attack/stimulate TSH receptors and mimic its effects.
• The thyroid then secretes more T3 and T4.
• Serum T4 is higher and serum TSH is lower than normal.
• Other features of hyperthyroidism are "overactive" signs and symptoms due to the body's hypermetabolic processes.
• Nervous and irritable, tremors, insomnia, emotionally labile, hallucinations, and paranoia
• Cardiovascular: tachycardia, increased afterload, sometimes HF due to increased heart workload
• Increased appetite, diarrhea, hair thinning, and hair loss (alopecia)
• Exophthalmus (bulging eyes), goiter (enlargement of the thyroid gland)

Additional Hyperthyroidism Symptoms and Thyroid Storm or Thyrotoxic Crisis

• Hypertrophy changes caused by autoantibodies and cells being stimulated causes a goiter
• Fatigue, weight loss, increased body temperature, heat intolerance, flushed, warm skin, and excessive sweating
• Thyrotoxic crisis is a hyperthyroid emergency can be caused by a stressor: infection, trauma, or surgery
• S & S:
  • Neuro: Restlessness, delirium, seizures, and coma
  • Circulatory: Severe tachycardia, heart failure, and shock
  • Other: Diaphoresis and hyperthermia (103-105 F)
• Treatment for hyperthyroidism includes:
  • Antithyroid meds that inhibit synthesis of thyroid hormones
  • Surgery such as a thyroidectomy (usually ~ 90 % removed)

Hypothyroidism

• Hypothyroidism is the state of deficient T3 and T4 production and release.
• Common disorder in the U.S. affecting 8% of women & 2% of men over 50.
• It is caused by congenital defects., direct removal of, or destroyed tissue(radiation)
• Autoimmune thyroiditis or Hashimoto's thyroiditis causes the autoantibodies to destroy thyroid tissue and is insidious.
• Endemic iodide deficiency may be prevalent in certain populations and/or geographical areas (not enough iodode in diet and thyroid synthesis drops).
• Overactivity of antithyroid drugs can cause hypothyroidism.

Hypothyroidism S&S

• Serum T4 will be lower than normal and TSH higher than normal
• S&S:
  • psych/CNS: confusion, slow speech & thinking, sluggish, memory loss, and depression.
  • Circulatory: anemia, bradycardia, decreased CO
  • Pulmonary: dyspnea, hypoventilation, CO2 retention
  • Gastrointestinal: decreased appetite, constipation
  • Dry and brittle hair that may fall out (alopecia)

Other Hypothyroid Symptoms And Extreme States

• Myxedema is where changes in the dermis cause water to get trapped under the skin.
• Skin course and dry.
• Goiter-in hypothyroidism is caused by two factors: hyperplasia & hypertrophy of the tissue and inflammation and eventual scar tissue from autoimmune attack.
• Weight gain despite decreased appetite.
• Decreased body temp and cold-intolerance.
• Extreme state: Myxedema coma or crisis brought on by stressor.
  • S&S: Hypothyroid sluggishness & drowsiness into gradual or sudden impaired consciousness and often hypotension and hypoventilation.
• Treatment: Synthetic thyroid hormone such as levothyroxine (Synthroid)

Notes on Goiter and Alopecia

• Goiter can occur in patients with both hyper and hypothyroidism.
• In hyperthyroidism the enlargement is a result of overactive cells.
• In hypothyroidism the enlargement is a result of compensatory change + scar tissue formation from inflammatory process.
• Alopecia can occur patients with both hyper and hypothyroidism.
• In hyperthyroidism the hair follicles become stressed by too much thyroid hormone.
• In hypothyroidism hair becomes dry and brittle, because of the lack of thyroid hormone.

Disorders of Calcium Movement

• Calcium is needed for bone density, cell electrical activity, clotting.
• Bone is the biggest storage area for calcium and it frequently is transferred to blood and back again.
• Hormones calcitonin & PTH are chief regulators of calcium movement.

Calcintonin

• Calcitonin secreted by the thyroid gland enhances calcium movement from blood into bone.
• Lowers bone resorption by decreasing osteoclastic activity.

Parathyroid Hormone (PTH)

• PTH increases movement of calcium from bone to bloodstream through increased osteoclastic activity
• Osteoclasts are cells that migrate along walls of capillaries in bones and break down bone cells to free calcium.
• Calcitonin & PTH work by negative feedback.
• Hypocalcemia causes secretion of PTH and suppressed calcitonin secretion.

Calcium Movements With Hypercalcemia and Hypocalcemia

• If more calcium is needed in the bone, calcitonin secretion is increased to create bone matrix, and PTH secretion is suppressed
• Osteoporosis: general term meaning pathologically “porous bone"
• Normally there is a balance between calcium in the bone and osteoclastic activity.
• Resorption increases with age leading to an exceeds of calcium into the blood so bone density increases.
• With less density the causes bone to become porous and is more likely to injure or fracture bones.

Risk Factors for Osteoporosis

• Women are more likely to have risk of osteoporosis due to two factors:
  • Women's bones are less dense than men's to begin with
  • Post-menopausal loss of estrogen
• Bone-building is maintained by estrogen
• Post-menopause decrease of estrogen = tipped toward more osteoclastic activity
• Osteopenia is the condition of having somewhat less normal bone density while osteoporosis is markedly lower.
• Bones more easily fractured, especially in the hip & vertebra.
• By age 80, one in 5 women will fracture a hip.
• If admitted to the hospital with a hip fracture, ~30% will die within the first year after surgery.

Hip Fracture Facts and Fat Emboli

• Fat emboli occur when a long bone is injured and fat is released to systemic circulation causing inflammation and ischemia.
• Sequelae in either osteopenia or osteoporosis includes: death
• Treatment: decreasing osteoclastic activity such as nasal calcitonin and biphosphonates.
• If hip is fracture have a surgery within 24 hours.
• electrical issues: hypo or hypercalcemia can affect Na+

Hypocalcemia and Hypercalcemia

• Clotting issues: Low calcium = low clotting ability, leads to easy bleeding, petechiae and purpura
• Can develop kidney stones.
• In hypoparathyroidism there is is decreased PTH and resorption of calcium
• Hyperparathyroidism or excess PTH leads to more resorption of calcium.
• Calcitonin hyposecretion leads to increased calcium resorption.
• Calcitonin secretion or decreased decreased resorption of calcium.
• Menopause can lead less bone-building because less osteclastic
• hypo and hyper calcium can affect electrical such positive Chvostek’s sign, renal calculi