Endocrine System Quiz

Endocrine System Disorders

• Disorders
  • Hyperthyroidism & Hypothyroidism
  • Addison's disease (adrenal hypofunction)
  • Cushing's syndrome
  • Diabetes insipidus
  • Diabetes mellitus
  • Syndrome of inappropriate antidiuretic hormone secretion (SIADH)

Endocrine Glands

• Components of the endocrine system
  • Pituitary gland
  • Thyroid gland
  • Parathyroid glands
  • Adrenal glands
  • Pancreas (endocrine and exocrine)
  • Reproductive organs (ovaries and testes)
  • Pineal gland
  • Hypothalamus

Gland Function

• Location & Function
  • Pituitary: Below the brain, controls other endocrine glands.
  • Thyroid: Front of neck (below larynx), plays a role in metabolism.
  • Parathyroid: Front of neck (below larynx), regulates calcium balance.
  • Adrenal: On top of kidneys, works with hypothalamus/pituitary, maintains blood pressure & regulates metabolism.
  • Pancreas: Across back of abdomen, behind stomach, role in digestion & hormone production (insulin and glucagon regulate blood sugar.)
  • Reproductive organs: Female and male reproductive system. Produce egg cells/estrogen/progesterone, testosterone/sperm.

Major Functions

• Regulates metabolism, reproduction, fluid/electrolyte balance, optimal internal environment (blood glucose regulation), and growth/development.

Hormones

• Action of hormones
  • Regulate homeostasis/reproduction/growth/development/metabolism
  • Delivered to receptors on their specific target organs (feedback loops maintain balanced hormone levels)
• Mechanism of secretion regulated by positive/negative feedback. Increased levels of one hormone inhibit the secretion, decreased level stimulates.

Hyperthyroidism

• Definition
  • Metabolic imbalance with overproduction of thyroid hormone (thyrotoxicosis).
  • A common form is Graves' disease.
• Causes
  • Excessive iodine intake
  • Defect in suppressor T-lymphocyte function (autoimmune)
  • Medications (like amiodarone)
  • Stress (surgery/infection/toxemia of pregnancy)
  • Nodules/tumors

Hyperthyroidism: Pathophysiology

• Mechanism
  • Autoimmune disorder where antibodies mimic the role of TSH, increasing thyroid hormone secretion.
  • Acute intoxication with exogenous hormones, or high iodine loads from drugs.
• Signs/Symptoms
  • Enlarged thyroid (goiter), apprehension, heart palpitations, weight loss, intolerance to heat/sweating.

Hypothyroidism

• Definition
  • Endocrine dysfunction with decreased/absent secretion of thyroid hormones.
• Causes
  • After thyroidectomy/radiation
  • Pituitary gland failure to produce TSH
  • Iodine deficiency
  • Medication

Hypothyroidism: Pathophysiology

• Mechanism

  • Primary: Thyroid injury from autoimmune disorder or adverse drug reaction.
  • Secondary: Damage to hypothalamus/pituitary gland causes decreased thyroid stimulation (decline in TSH production/release)

• Signs/Symptoms

  • Weakness/fatigue/forgetfulness/sensitivity to cold/unexplained weight gain/coarse hair/skin, neurological changes, cardiovascular symptoms.

Addison's Disease (Adrenal Hypofunction)

• Definition
  • Adrenal gland hypofunction.
• Types
  • Primary: From within the gland (e.g., adrenalectomy), decreased secretion of mineralocorticoids/glucocorticoids/androgens.
  • Secondary: From outside the gland (e.g., impaired pituitary secretion), decreased glucocorticoid secretion.
• Pathophysiology Involves all zones of the cortex, causing deficiencies in adrenocortical secretions, causing low blood glucose. Aldosterone deficiency causes increased renal sodium loss & enhances potassium reabsorption & androgen deficiency can decrease hair growth in armpits and pubic areas.
• Signs and Symptoms
  • Hyperpigmentation/low blood sugar/fatigue/malaise/loss of appetite/addisonian crisis (life-threatening physical stress & trauma)

Cushing's Syndrome

• Definition
  • A cluster of clinical abnormalities caused by excessive adrenocortical hormones (especially cortisol).
• Causes
  • Anterior pituitary hormone (corticotropin) excess
  • Autonomous, ectopic corticotropin secretion by a tumor; excessive glucocorticoid administration (prolonged use).
• Pathophysiology
  • Prolonged excess glucocorticoids; cortisol excess results in anti-inflammatory effects & excessive catabolism of protein/peripheral fat to support hepatic glucose production. Excess cortisol suppresses the hypothalamic-pituitary-adrenal axis.
• Signs and Symptoms
  • Diabetes mellitus, muscle weakness, purple striae/facial plethora, buffalo hump/moon face/truncal obesity.

Diabetes Insipidus

• Definition
  • Water metabolism disorder; deficiency of circulating vasopressin (ADH) or renal resistance to ADH.
• Causes
  • Acquired, familial, idiopathic, neurogenic, or nephrogenic
  • Associated with stroke, hypothalamic/pituitary tumors, cranial trauma or surgery; certain drugs (like lithium).
• Pathophysiology Neurogenic is inadequate response to ADH in response to plasma osmolarity. Nephrogenic diabetes insipidus is due to inadequate renal response to ADH. Psychogenic is due to extremely large fluid intake.
• Signs/Symptoms
  • Polydipsia/polyuria (urine output 2-20 L/day)/Nocturia/sleep disturbance/fatigue/ low urine specific gravity (< 1.006).

Diabetes Mellitus

• Definition -Metabolic disorder; characterized hyperglycemia due to lack of insulin, lack of insulin effect, or both.
• Types
  • Type 1: Absolute insulin insufficiency
  • Type 2: Insulin resistance with varying degrees of insulin secretory defects
  • Gestational: Glucose intolerance during pregnancy.
• Causes
  • Environmental factors (infection/diet/toxins/stress)
  • Heredity
  • Lifestyle changes

Diabetes Mellitus: Pathophysiology

• Type 1 triggering event (possibly viral) causes production of autoantibodies against beta cells of pancreas, leading to insulin deficiency.
• Type 2 is a chronic disease due to impaired insulin secretion, inappropriate hepatic glucose production, or peripheral insulin receptor insensitivity.
• Gestational occurs when placental hormones oppose insulin action leading to insulin resistance.
• Signs and Symptoms
  • Polyuria/polydipsia/polyphagia/weight loss/thirst/blurred vision/fatigue.

Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH)

• Definition
  • A condition where the body produces too much antidiuretic hormone (ADH).
• Pathophysiology
  • Excessive ADH leads to excessive water reabsorption from the distal convoluted tubule & collecting ducts which causes hyponatremia/normal to slightly increased extracellular fluid volume. This can lead to cerebral edema, brain herniation.
• Causes
  • Oat cell carcinoma/drugs that increase/potentiate ADH/central nervous system disorders/brain tumor/brain injury, infections, stroke.
• Signs/Symptoms
  • Thirst/anorexia/fatigue/lethargy/weight gain/edema/water retention, decreased urine output/hyponatremia.