Exam 4 · Week 8 · BIO 280 Pathophysiology
M8 · Endocrinology & Endocrine Disorders
Feedback loops, and the six gland pairs where too much and too little are mirror images of each other.
▸M8Endocrinology & Endocrine DisordersWeek 8
💡 The one idea
Nearly every endocrine disease is one gland doing too much or too little, and the two are mirror images. Learn one side properly and you get the other for free.
Negative feedback: the product switches off its own signal. If the product is high and the signal is also high, the problem is the gland giving the signal.
🔄 How the axis works
Hypothalamus → pituitary → target gland → hormone. The hormone then feeds back and turns the top of the chain off.
- Primary problem = the target gland itself. Hormone low, and the pituitary signal (TSH, ACTH) is high because it is shouting at a gland that cannot answer.
- Secondary problem = the pituitary. Hormone low and the signal is low too.
Both numbers low → the problem is upstream. One low, one high → the problem is the gland.
🧘 Thyroid — the whole body's thermostat
| Hypothyroid | Hyperthyroid | |
|---|---|---|
| Everything is | Slow and cold | Fast and hot |
| Signs | Fatigue, weight gain, cold intolerance, constipation, dry skin, hair loss, bradycardia, depression, menorrhagia | Weight loss with good appetite, heat intolerance, diarrhea, tremor, tachycardia, anxiety, insomnia, exophthalmos in Graves |
| TSH (primary) | High | Low |
| T3 / T4 | Low | High |
| Crisis | Myxedema coma — hypothermia, hypotension, bradycardia, unresponsive | Thyroid storm — fever >38.5, tachycardia,
agitation, delirium |
TSH moves opposite to the thyroid hormone in primary disease. That inverse is the single most tested relationship in the module.
🦵 Parathyroid and calcium
PTH raises serum calcium — it pulls it from bone, reabsorbs it in the kidney, and activates vitamin D to absorb it from the gut. Phosphate moves the opposite way.
- Hyperparathyroid → high calcium → stones, bones, groans and moans: renal calculi, bone pain and fractures, constipation and abdominal pain, lethargy and confusion. Reflexes are depressed.
- Hypoparathyroid → low calcium → irritable everything: tetany, perioral tingling, muscle cramps, Chvostek and Trousseau signs, and the one that kills — laryngospasm. Reflexes are brisk.
After thyroid or parathyroid surgery, hoarseness, tingling around the mouth or stridor means the calcium has crashed. Keep calcium gluconate available.
🚨 Adrenal — Cushing vs Addison
| Cushing (too much cortisol) | Addison (too little) | |
|---|---|---|
| Body | Central obesity, moon face, buffalo hump, thin limbs, purple striae, thin skin, bruising | Weight loss, fatigue, anorexia, bronze hyperpigmentation |
| Sodium / water | Retained — hypertension, edema | Lost — hypotension, dehydration |
| Potassium | Low | High |
| Glucose | High | Low |
| Immunity | Suppressed — infection risk, poor healing | — |
Addisonian crisis — profound hypotension, hyperkalemia, hypoglycemia and shock, often triggered by stress, infection, or abruptly stopping steroids. Long-term corticosteroids must always be tapered, never stopped suddenly.
⭐ Diabetes — and the two emergencies
| Type 1 | Type 2 | |
|---|---|---|
| Problem | No insulin — autoimmune beta-cell destruction | Insulin resistance plus relative deficiency |
| Onset | Usually young, abrupt | Usually adult, gradual |
| Ketones | Yes — DKA | Rarely — HHS instead |
The three Ps: polyuria, polydipsia, polyphagia. Glucose spills into the urine and drags water with it.
| DKA | HHS | |
|---|---|---|
| Insulin | None | A little — enough to block ketones |
| Glucose | >250 | >600 |
| pH | Acidotic | Normal |
| Hallmark | Kussmaul respirations, fruity breath, abdominal pain | Profound dehydration and neurological change |
| Onset | Hours | Days |
Treatment order for both: fluids first, then insulin — and check the potassium
before the insulin. Acidosis has driven potassium out of the cells, so serum potassium
can look normal while total body potassium is depleted; insulin drives it back in and the
level can fall far enough to stop the heart. At a glucose of ~250, add dextrose
and keep the insulin running — the insulin is there to switch off ketone production,
not only to lower the number.
🎯 Module quiz
Questions for this module.
Nothing here yet — drop it in when you have it