09/07/2026
Endocrine System Study Notes 🧠🦋
Think of the endocrine system as the body’s chemical communication network. Endocrine glands release hormones directly into the bloodstream, affecting metabolism, growth, reproduction, stress response, fluid balance, and blood glucose.
🧠 Hypothalamus
The hypothalamus connects the nervous system to the endocrine system and controls the pituitary through releasing/inhibiting hormones. It also helps regulate temperature, hunger, thirst, sleep, and circadian rhythm.
👑 Pituitary gland — “Master gland”
Anterior pituitary: remember FLAT PiG
* FSH → reproduction
* LH → ovulation/testosterone production
* ACTH → stimulates adrenal cortex → cortisol
* TSH → stimulates thyroid
* Prolactin → milk production
* GH → growth
Posterior pituitary releases:
* ADH/vasopressin → retains water
* Oxytocin → uterine contractions and milk ejection
Important: ADH and oxytocin are made in the hypothalamus and stored/released from the posterior pituitary.
🦋 Thyroid
Produces T3 and T4, which increase metabolic activity. It also produces calcitonin, which tends to lower serum calcium.
Hypothyroidism = everything slows down: fatigue, weight gain, cold intolerance, constipation, bradycardia.
Hyperthyroidism = everything speeds up: weight loss, heat intolerance, sweating, tachycardia, tremor, anxiety.
🚨 Thyroid storm is an emergency: severe hyperthermia, marked tachycardia and altered mental status.
🦴 Parathyroid glands
Produce PTH (parathyroid hormone).
⭐ PTH raises serum calcium.
Low calcium can cause tingling, muscle cramps, tetany, Chvostek sign and Trousseau sign.
⚡ Adrenal glands
Adrenal cortex: remember Salt, Sugar, S*x
* Aldosterone = salt → sodium retention, potassium excretion
* Cortisol = sugar/stress
* Androgens = s*x hormones
Adrenal medulla: releases epinephrine and norepinephrine → fight-or-flight response.
🍬 Pancreas
The pancreatic islets regulate blood glucose.
Beta cells → Insulin → ↓ blood glucose
Alpha cells → Glucagon → ↑ blood glucose
Think: Insulin puts glucose INTO cells.
🚨 Hypoglycemia: sweating, shakiness, hunger, confusion, tachycardia. Severe cases can cause seizures or unconsciousness.
🚨 Hyperglycemia: polyuria, polydipsia, dehydration and blurred vision.
💧 ADH disorders
SIADH = too much ADH
→ water retention
→ dilutional hyponatremia
→ concentrated urine
Diabetes insipidus = too little ADH or poor renal response
→ very large amounts of dilute urine
→ intense thirst
→ dehydration
→ possible hypernatremia
⭐ Easy memory:
SIADH = Save water
DI = Dry Inside
🩺 Adrenal disorders
Cushing syndrome = too much cortisol
→ hyperglycemia, hypertension, muscle weakness, increased infection risk, central weight gain and characteristic fat redistribution.
Adrenal insufficiency/Addison disease = too little cortisol ± aldosterone
→ hypotension, weakness, weight loss, hyponatremia and, in primary disease, often hyperkalemia.
🚨 Adrenal crisis can cause profound hypotension/shock and requires emergency treatment.
🧪 High-yield endocrine labs
Know how to interpret:
TSH • Free T4 • Blood glucose • HbA1c • Sodium • Potassium • Calcium • Cortisol • Serum/urine osmolality
⭐ NCLEX Quick Memory
T3/T4 → Metabolism
PTH → ↑ Calcium
Calcitonin → ↓ Calcium
Insulin → ↓ Glucose
Glucagon → ↑ Glucose
ADH → Retains water
Aldosterone → Retains Na⁺, excretes K⁺
Cortisol → Stress response
Epinephrine → Fight or flight
NCLEX priority: Endocrine emergencies can quickly become airway, circulation, glucose, fluid, or electrolyte emergencies—prioritize ABCs, neurological status, glucose, vital signs, and critical electrolyte abnormalities.