Endocrine System Notes

Endocrine System vs. Nervous System

• Endocrine System:
  • Hormones travel through the bloodstream.
  • Slower transmission.
  • Effects are longer-lasting.
• Nervous System:
  • Uses neurotransmitters.
  • Faster transmission via synapses.
  • Effects are short-lived.

Endocrine vs. Exocrine Glands

• Endocrine Glands: Secrete fluids into the bloodstream.
  • Examples: pituitary, pineal, thyroid, adrenal glands.
• Exocrine Glands: Secrete substances through ducts onto the body surface.
  • Examples: sweat, tears, saliva, breast milk (mammary glands).
  • These are not part of the endocrine system.

Hypothalamus

• Control center that receives input and decides whether to act.
• Hypothalamic-Pituitary Portal System: Secretes ADH (antidiuretic hormone) and oxytocin.
• Posterior pituitary is an extension of the hypothalamus.
• Functions:
  • Autonomic center (subconscious facial expressions).
  • Regulates circadian rhythms, mood, sleep cycles, temperature.
  • Controls the "five F's": fight, flight, food, fun, fornication.
• Hormones travel throughout the body.
• HPA Axis: Secretes ADH and oxytocin, stored in the posterior pituitary.

Pituitary Gland

• Master gland impacting various bodily functions.

  • Anterior Pituitary (Adenohypophysis): Controlled by the hypothalamus.
  • Most common reason for too much hormone secretion is an adenoma.

• Anterior Pituitary Hormones

  • Growth hormone.
  • Prolactin.
  • ACTH (adrenocorticotropic hormone).
  • TSH (thyroid-stimulating hormone).
  • FSH (follicle-stimulating hormone).
  • LH (luteinizing hormone).

• Posterior Pituitary Hormones

  • Produced in the hypothalamus and stored in the posterior pituitary (nerve extensions).
  • ADH (antidiuretic hormone): Conserves fluid by reducing water passed in urine.
  • Oxytocin.

Hormone Destinations

• FSH: Ovaries.
• FSH & LH: Testes.
• Growth Hormone: Bone, skin.
• Prolactin: Mammary glands.
• ACTH: Adrenal glands.
• TSH: Thyroid.
• Oxytocin: Mammary glands, uterus.
• ADH: Kidney.

Feedback Loops

• Negative Feedback:
  • Allows the endocrine system to self-regulate.
  • Stops hormone production once homeostasis is reached.
  • Example: Thermostat sensing temperature and generating heat until the desired temperature is reached.
• Positive Feedback:
  • Keeps the stimulus going until resolution.
  • Examples:
    • Labor and childbirth: Continues until the baby is born.
    • Blood clotting: Continues until bleeding stops.
• Goal: Maintain homeostasis.
• Most hormones use negative feedback.
• Oxytocin is an example of positive feedback.

Pineal Gland

• Receives information on light and dark cycles, releases melatonin.
• Dysfunction can lead to sleep disturbances.
• Signs/Symptoms: Headaches, seizures, memory disturbances, visual changes, nausea, vomiting.

Endocrine vs. Nervous System (Revisited)

• Endocrine System:
  • Hypothalamus communicates with anterior pituitary, which affects target organs (gonads, adrenal cortex, thyroid, mammary glands, liver).
  • Long pathways.
• Nervous system
  • Neurons in the Hypothalamus send the signal through the posterior pituitary through nerves
  • Release of oxytocin and ADH.
  • ADH goes to kidney.
  • Oxytocin goes to mammary gland.

Hormone Secretion Issue

• If pituitary adenoma releases excessive ACTH, expect high cortisol levels from the adrenal gland.

Levels of Endocrine Dysfunction

• Tertiary: Dysfunction caused by the hypothalamus (rare).
  • Example: Hypothyroidism due to lack of TRH.
• Secondary: Dysfunction caused by the pituitary.
  • Example: Hypothyroidism due to lack of TSH.
• Primary: Dysfunction of the endocrine gland itself.
  • Example: Hyperthyroidism due to an autoimmune disease affecting the thyroid.

Adrenal Gland

• Located on top of the kidneys.
• Contains the cortex and medulla.
• Releases corticosteroids (GMA):
  • Glucocorticoids (Sweet):
    • Stimulate fat and carbohydrate metabolism.
    • Decrease inflammation reduce activity in the immune system.
    • Regulate blood glucose; act on the pancreas with insulin.
  • Mineralocorticoids (Salty):
    • Maintain blood pressure (e.g., aldosterone).
  • Androgens (Sex).
• Adrenal Medulla:
  • Stimulated by the sympathetic nervous system.
  • Releases dopamine, epinephrine, and norepinephrine.

Cushing's Syndrome

• Characterized by excess cortisol.
• Causes:
  • Taking too many glucocorticoids (e.g., prednisone).
  • Adrenal adenoma.
  • Pituitary adenoma (excess ACTH).
• Signs/Symptoms:
  • Weight gain / Obesity.
  • Buffalo hump.
  • Moon face.
  • Purple striae (thick stretch marks).
  • Hypertension.
  • Hyperglycemia.
  • Muscle wasting.
  • Protein breakdown.
  • Thin, fragile skin.
  • Recurrent infections.

Addison's Disease

• Autoimmune disease that destroys the adrenal gland, resulting in low cortisol levels.
• Signs/Symptoms:
  • Darker skin (hyperpigmentation) due to excessive ACTH, patchy and splashy, not a bronzed tan.
  • GI disturbances (nausea, vomiting).
  • Weight loss.
  • Hypotension.
  • Hypoglycemia.
  • Hair loss.
  • Blurry vision.
  • Abdominal pain.
  • Decreased appetite.
  • Shaking.
  • Depression.

HPA Axis and Disease

• H (Hypothalamus): Tertiary - Damage to the hypothalamus.
• P (Pituitary): Secondary - Damage to the pituitary.
• A (Adrenal Gland): Primary - Damage to the adrenal gland (target organ).
• Addison's disease is primary.

Steroid Management

• Never abruptly stop steroids!
• Steroids suppress natural hormone generation.
• Gap time when stopping steroids leads to Addisonian crisis (adrenal insufficiency).
• Addisonian Crisis: Hypotension, weakness, hypoglycemia, hyponatremia, hyperkalemia.
• Adrenal insufficiency is life-threatening.

Adrenal Insufficiency

• Low Cortisol:
  • Impacts liver function and glucose levels, leading to coma and death.
• Low Aldosterone:
  • Impacts kidneys, heart, and blood pressure.
  • Leads to shock, low digestive enzymes, vomiting, diarrhea, cramps.

HPA Axis Examples

• Example 1: Pituitary adenoma causing excessive ACTH
  • Issue: Pituitary (Secondary endocrine disease).
  • ACTH: Increased (up arrow).
  • Adrenal gland produces excessive corticosteroid.
  • High corticosteroid shuts off the hypothalamus.
• Example 2: Autoimmune disease destroying the adrenal gland
  • Issue: Adrenal gland (Primary).
  • Corticosteroid: Decreased.
  • Hypothalamus: Increases CHR.
  • Pituitary: Increases ACTH.

Pheochromocytoma

• Pheno (dark), Chromo (color), Cyte (cell), Oma (tumor).
• Rare tumor (90% benign).
• Inappropriate activation of "flight or fight" response.
• Episodic (paroxysmal).
• Tumor of chromaffin cells in the adrenal medulla.
• High levels of catecholamines (epinephrine, norepinephrine, dopamine).
• Excessive sympathetic activation.
• Symptoms: Hypertension, weight loss, hyperglycemia, headaches.
• Paroxysmal Symptoms: Sudden onset headache, diaphoresis, pallor, palpitations, anxiety, tachycardia, abdominal pain, nausea, flushing, tremors.

Thyroid Gland Review

• Regulates metabolic functions, heart rate/rhythm, muscle contraction, weight, energy levels, temperature, skin, hair, nails, cognitive capacity.
• TSH (thyroid stimulating hormone).
• Hypothyroidism: Low T3 and T4, high TSH (due to the negative feedback system).

Thyroid Imbalances

• Hypothyroidism:
  • Most common cause: Autoimmune destruction of the thyroid gland (Hashimoto's thyroiditis), leading to lack of T3 and T4.
  • Feedback Loop: Low T3/T4, high TRH/TSH.
  • Everything slows down.
  • Myxedema coma: Severe condition progressing to confusion and coma.
  • Symptoms: Cold intolerance, dry hair, puffy face, goiter, slow heartbeat, weight gain, constipation.
• Hyperthyroidism:
  • Everything is sped up.
  • Most common cause: Graves' disease (autoantibodies target TSH receptors).
  • Thyrotoxic crisis/storm: Life-threatening condition with elevated thyroid hormones.
  • Symptoms: Heat intolerance, rapid heartbeat, weight loss, bulging eyes.

Goiters

• Enlarged/swollen thyroid gland (with or without symptoms).
• Causes: Hypo or hyperthyroidism, Graves' disease, iodine deficiency.
• Can be caused by low circulating T4 with elevated TSH (hypothyroidism).
• Graves' disease involves excessive antibody attack on TSH secretion (hyperthyroidism).
• Iodine deficiency is a common cause in developing nations.

Hypoparathyroidism

• Can be caused by trauma, surgical removal (thyroidectomy), or genetic disorder.
• Worried about the release of calcium from bones into the bloodstream.
• Low calcium symptoms: CATS (convulsions, arrhythmias, tetany, spasms, stridor).
• Chebostik (facial muscle twitch) and Trousseau (carpal spasm) signs.
• Symptoms: Tingling of toes, muscle spasms.

Growth Hormone (Somatotropin)

• Functions: Cell growth, protein synthesis, lipid mobilization, anabolic (promotes growth of skeletal muscle, bone, cartilage).
• Causes of low somatotropin: Dwarfism (genetic defects, brain injury, congenital).
• Pituitary adenoma is the most common cause of excessive pituitary hormones.
• Treatment: Transsphenoidal surgery.
• Dwarfism: Short stature, small hands, but proportionate body features, delayed puberty.

Growth Hormone Excess

• Excessive Levels: Giantism or Acromegaly.
• Giantism: Excessive GH prior to growth plate fusion;
• Acromegaly: Excessive GH after growth plate fusion.
• Acromegaly: Large nose, large jaw, large hands/feet/tongue, prominent eyebrows, hypertension, hypercholesterolemia, congestive heart failure, arthritis, bone deformities, diabetes, headaches, vision problems.

ADH (Antidiuretic Hormone)

• Osmolality: The concentration of solutes in a solution (use urine or blood).
• Specific Gravity: Measurement of urine concentration.
• SIADH (Syndrome of Inappropriate Antidiuretic Hormone):
  • Excessive ADH leads to excessive water reabsorption (soaked on the inside).
  • Elevated blood pressure.
  • Hyponatremia symptoms: Irritable, confused, headache, muscle cramps, twitching.
  • Concentrated urine, high specific gravity, high urine osmolality, edema.
  • Low serum osmolality (due to excess fluid in blood vessels).
• Diabetes Insipidus (DI):
  • Not the same as diabetes mellitus, but both increase urine output and thirst.
  • No ADH leads to excessive water loss (DI = Dry Inside).
  • Leads to excessive urination.
  • Diluted urine, dry skin.
  • Hypernatremia, dehydration, thirst, low urine specific gravity, fatigue, seizures, coma, muscle twitching.

Diabetes Mellitus

• Increases the risk of stroke, peripheral vascular disease, and kidney damage.
• Insulin: Hormone that regulates blood glucose (key for glucose to enter cells).
• Glucagon: Hormone secreted by alpha cells when glucose is low.
• Insulin is secreted by beta cells in the pancreatic islets of Langerhans.
• Role of Insulin: To allow glucose to be used as energy and maintain the glucose in the bloodstream with normal limits
• Insulin allows glucose to enter the cells, moves potassium into the cell, and prevents fat breakdown.

Diabetes Type 1

• Autoimmune condition destroying pancreatic beta cells.
• No insulin means glucose can't be stored, leading to elevated serum glucose and glucose in the urine.
• Hemoglobin A1c: Measures percentage of sugar-coated hemoglobin (glycated) over 3 months (used for both type 1 and type 2).
• Symptoms: Polyuria, polydipsia, dehydration, DKA (diabetic ketoacidosis), Kussmaul's breathing, polyphagia, blurry vision, weight loss.

Diabetes Type 2

• Cells become resistant or desensitized to the available insulin.
• Risk Factors: Age, inactivity, history of gestational diabetes, poor diet, adipose tissue.
• Beta cells are working normally, but body cells are resistant to insulin.
• Insensitivity to insulin causes the pancreas to try compensating by secreting increasing amounts of the insulin.
• Secondary impacts: Treatment is diet, exercise, weight loss, oral medications, and insulin.
• Hyperosmolar hyperglycemic syndrome (HHS).
• Symptoms: Hyperglycemia, fatigue, weakness, blurry vision.

HHS vs. DKA

• HHS (Hyperosmolar Hyperglycemic Syndrome)
  • More common in type 2 diabetes.
  • Blood sugar level of 600 or higher.
  • Blood becomes thick (profoundly dehydrated).
  • Osmotic diuresis.
  • Symptoms : Polydipsia, polyuria, dehydrated, drowsiness, confusion
• DKA (Diabetic Ketoacidosis)
  • blood sugar less than 250
  • Acetone, ketones, pH, Kussmauls develops quickly.
  • Emergency take people to the hospital for DKA.
    major complicationsMicrovascular (eye, kidneys, neuropathy)Macrovascular (brain, heart, extremities)Increased risk of stroke, peripheral

Gestational Diabetes

• Insulin resistance in pregnant women who can't produce enough insulin during late pregnancy.
• Higher risk of developing type 2 later on.
• Macrosomnia (large baby, increased birth weight).
• Possible preterm labor (before 36 weeks) and delayed lung development in the baby.
• Maternal hormonal changes during pregnancy affect pancreas.
• Pregnancy hormones can affect the pancreas, and as the baby grows, her body produces more homrones. is a thing.