Chapter Overview & Weightage
Chemical Coordination covers endocrine glands, hormones, their target organs, feedback mechanisms, and hormonal disorders. This is a high-scoring chapter because questions are direct — gland-hormone-function matching is all you need for most marks.
This chapter carries 4-5% weightage in NEET with 3-4 questions. Gland-hormone-function matching and hormonal disorder identification are the bread and butter of this chapter.
Key Concepts You Must Know
Tier 1 (Core)
- Hypothalamus: releasing/inhibiting hormones that control the anterior pituitary
- Pituitary gland: anterior (GH, TSH, ACTH, FSH, LH, PRL) and posterior (ADH/vasopressin, oxytocin)
- Thyroid: T3, T4 (metabolism regulation), calcitonin (lowers blood Ca)
- Parathyroid: PTH (raises blood Ca) — antagonistic to calcitonin
- Adrenal gland: cortex (cortisol, aldosterone, androgens) and medulla (adrenaline, noradrenaline)
- Pancreas (endocrine): insulin (lowers blood glucose, beta cells) and glucagon (raises blood glucose, alpha cells)
Tier 2 (Frequently tested)
- Feedback mechanism: negative feedback loop (e.g., high T3/T4 → inhibits TSH release)
- Hormonal disorders: diabetes mellitus, goitre, dwarfism, gigantism, acromegaly, Addison’s disease, Cushing’s syndrome
- Pineal gland: melatonin (regulates sleep-wake cycle)
- Thymus: thymosin (T-cell maturation, degenerates with age)
Tier 3 (Occasionally tested)
- Mechanism of hormone action: peptide hormones (membrane receptors, second messenger cAMP) vs steroid hormones (intracellular receptors, gene regulation)
- Gastrointestinal hormones: gastrin, secretin, CCK
- Erythropoietin from kidneys, ANF from heart
Important Formulas
| Gland | Hormone | Key Function |
|---|---|---|
| Hypothalamus | GnRH, TRH, CRH, GHRH, somatostatin | Controls anterior pituitary |
| Anterior pituitary | GH, TSH, ACTH, FSH, LH, PRL | Master gland (growth, reproduction, other glands) |
| Posterior pituitary | ADH, Oxytocin | Water balance, uterine contraction |
| Thyroid | T3, T4, Calcitonin | BMR regulation, Ca lowering |
| Parathyroid | PTH | Ca raising |
| Adrenal cortex | Cortisol, Aldosterone | Stress response, Na/K balance |
| Adrenal medulla | Adrenaline, Noradrenaline | Fight-or-flight response |
| Pancreas (beta) | Insulin | Lowers blood glucose |
| Pancreas (alpha) | Glucagon | Raises blood glucose |
| Gonads | Estrogen, Progesterone, Testosterone | Reproductive functions |
| Pineal | Melatonin | Sleep cycle |
| Thymus | Thymosin | T-cell maturation |
| Disorder | Cause | Key Symptoms |
|---|---|---|
| Diabetes mellitus | Insulin deficiency/resistance | High blood glucose, polyuria |
| Goitre | Iodine deficiency → low T3/T4 | Enlarged thyroid |
| Cretinism | Hypothyroidism in childhood | Stunted growth, mental retardation |
| Dwarfism | GH deficiency in childhood | Short stature, normal proportions |
| Gigantism | GH excess in childhood | Excessive height |
| Acromegaly | GH excess in adults | Enlarged hands, feet, jaw |
| Addison’s disease | Adrenal cortex hypofunction | Low BP, weakness, darkened skin |
| Cushing’s syndrome | Cortisol excess | Moon face, obesity, high BP |
NEET loves the insulin-glucagon pair. Remember: Insulin = Into cells (glucose moves into cells, blood sugar drops). Glucagon = Glucose out (from liver glycogen into blood, blood sugar rises). They’re antagonistic hormones from the same gland.
Solved Previous Year Questions
PYQ 1 — NEET 2024
Problem: Which hormone is called the “emergency hormone”?
(A) Insulin (B) Thyroxine (C) Adrenaline (D) Cortisol
Solution:
Adrenaline (epinephrine) from the adrenal medulla is the emergency/fight-or-flight hormone. It increases heart rate, dilates bronchi, raises blood pressure, diverts blood to muscles, and triggers glycogenolysis — all preparing the body for emergency action.
Answer: (C) Adrenaline
PYQ 2 — NEET 2023
Problem: Acromegaly is caused by:
(A) Excess GH in childhood (B) Excess GH in adults (C) Deficiency of GH (D) Excess TSH
Solution:
- Excess GH in childhood (before growth plates close) → gigantism
- Excess GH in adults (after growth plates close) → acromegaly (disproportionate growth of extremities and jaw)
- Deficiency of GH in childhood → dwarfism
Answer: (B) Excess GH in adults
PYQ 3 — NEET 2022
Problem: Calcitonin and PTH are antagonistic with respect to:
(A) Blood glucose (B) Blood calcium (C) Blood pressure (D) Body temperature
Solution:
Calcitonin (from thyroid parafollicular/C cells) lowers blood Ca by promoting calcium deposition in bones and reducing intestinal absorption.
PTH (from parathyroid glands) raises blood Ca by promoting bone resorption, increasing renal reabsorption, and activating Vitamin D for intestinal absorption.
They’re antagonistic for blood calcium regulation.
Answer: (B) Blood calcium
Calcitonin = Calcium tones down (lowers). PTH = Parathyroid Hormone = Pushes calcium up (raises). Don’t confuse which one raises and which one lowers. The mnemonic in the names helps.
Difficulty Distribution
| Difficulty | % of Questions | What to Expect |
|---|---|---|
| Easy | 50% | Gland-hormone matching, disorder identification |
| Medium | 35% | Feedback mechanism, antagonistic hormone pairs |
| Hard | 15% | Mechanism of hormone action, second messenger system |
Expert Strategy
Day 1: Build the master gland-hormone-function table. There are about 20 hormones NEET cares about. Use flashcards to drill gland → hormone → function chains.
Day 2: Hormonal disorders — match each disorder to its hormonal cause. Most questions give symptoms and ask for the disorder or the hormone involved. Know the key symptom for each disorder.
Day 3: Feedback mechanisms and antagonistic pairs (insulin-glucagon, calcitonin-PTH, T3/T4-TSH). Understand how the hypothalamus-pituitary axis works as a master control system.
NEET has started asking about non-traditional endocrine organs: kidneys (erythropoietin), heart (ANF), GI tract (gastrin, secretin, CCK). Know at least 2-3 hormones from these “non-gland” sources. These fetch easy marks because most students skip them.
Common Traps
Trap 1 — ADH is produced by the hypothalamus, not the posterior pituitary. The posterior pituitary only stores and releases ADH and oxytocin. They’re synthesised in the hypothalamic nuclei and transported via axons to the posterior pituitary for release.
Trap 2 — Alpha cells produce glucagon, beta cells produce insulin. Don’t swap them. Alpha = glucAGON (A for Alpha). Beta = insulin.
Trap 3 — Goitre can be caused by both hypo- and hyperthyroidism. Simple goitre is from iodine deficiency (hypothyroidism). But Graves’ disease (hyperthyroidism) also causes thyroid enlargement. NEET usually tests the iodine deficiency type.
Trap 4 — Thymus degenerates with age. It’s most active in childhood (for T-cell maturation) and atrophies in adults. This is why elderly people have weaker immune responses. NEET tests the age-related degeneration of thymus specifically.