BiologyISC Class 11 · Chemical Coordination and Integration

Hypothalamus, Pituitary Gland, Feedback Control and Mechanism of Hormone Action

Updated 17 October 2026 · Fact-checked

Hormones are chemical messengers made by endocrine glands in small amounts and carried by blood. The hypothalamus controls the pituitary through releasing and inhibiting hormones. The anterior pituitary makes GH, PRL, TSH, ACTH, LH and FSH; the posterior pituitary stores oxytocin and vasopressin made by the hypothalamus. Peptide hormones act through second messengers such as cAMP; steroid hormones act on intracellular receptors.

Notice the anterior pituitary is controlled by hormones through blood vessels, while the posterior pituitary releases hormones made in the hypothalamus.

Illustration drawn for QuestionBuddy.

Understand Hypothalamus, Pituitary and Hormone Action

Hormones. Non-nutrient chemicals that act as intercellular messengers, produced in trace amounts. Classes: peptide, polypeptide and protein hormones (pituitary, pancreas, hypothalamus), steroids (cortisol, testosterone, oestradiol, progesterone), iodothyronines (thyroid hormones) and amino acid derivatives (adrenaline).

Hypothalamus. Contains neurosecretory cells that produce releasing hormones (stimulating the pituitary, e.g. GnRH) and inhibiting hormones (somatostatin, which inhibits GH release). They reach the anterior pituitary through the hypophyseal portal system. The posterior pituitary is connected to the hypothalamus by nerve axons.

Anterior pituitary (adenohypophysis). *Growth hormone (GH):* hypersecretion in childhood causes gigantism, in adults acromegaly; hyposecretion in childhood causes pituitary dwarfism. *Prolactin (PRL):* growth of mammary glands and milk formation. *TSH:* stimulates the thyroid. *ACTH:* stimulates the adrenal cortex. *LH and FSH (gonadotropins):* LH stimulates testosterone synthesis (Leydig cells) and ovulation; FSH stimulates spermatogenesis and follicle growth.

Posterior pituitary (neurohypophysis). Stores and releases two hormones made in the hypothalamus: *oxytocin* (contraction of uterine smooth muscle during childbirth and milk ejection) and *vasopressin* or ADH (water reabsorption in the kidney; its deficiency causes diabetes insipidus with excessive dilute urine).

Pineal gland. Secretes melatonin, which regulates the sleep-wake cycle (diurnal rhythm), body temperature and menstrual cycle.

Feedback control. A rise in the hormone of the target gland inhibits the hypothalamus and pituitary (negative feedback): for example, TRH → TSH → thyroid hormones, which inhibit TRH and TSH release.

Mechanism of action. Hormones bind to specific receptors on target cells. Protein and peptide hormones bind to membrane receptors, activating second messengers (cAMP, Ca²⁺, IP₃) that change enzyme activity and metabolism. Steroid and thyroid hormones enter the cell, bind intracellular receptors, and the complex alters gene expression.

Hypothalamus, Pituitary and Hormone Action: key facts

Anterior pituitary: $G H ∣ P R L ∣ T S H ∣ A C T H ∣ L H ∣ F S H$; Controlled by hypothalamic hormones.
Posterior pituitary: $O x y t oc in ∣ V a so p r ess in (A D H)$; Made in the hypothalamus.
Disorders of GH: $G i g an t i s m (c hi l d) ∣ A cr o m e g a l y (a d u l t) ∣ D w a r f i s m (h y p osecr e t i o n)$; Linked to the amount of GH.
Hormone action: Peptide: membrane receptor + cAMP | Steroid: intracellular receptor + gene; Second messenger versus gene expression.

Hypothalamus, Pituitary and Hormone Action in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

An unusually tall teenager

Suppose a boy grows far taller than his age group and a scan shows a tumour of the anterior pituitary.

Name the hormone and the condition, and say what would happen if the tumour appeared after adulthood.

Try it first, then show the solutionSolution

The tumour secretes too much growth hormone (GH).
In childhood, before the growth plates close, this causes gigantism.
In an adult, the long bones cannot grow longer, so the hands, feet and facial bones enlarge, the condition called acromegaly.

Answer: Excess GH: gigantism in childhood and acromegaly in adults.

Memory hook: The age at which GH rises decides the condition.

Tricks to remember Hypothalamus, Pituitary and Hormone Action

Short memory aids. Say each one aloud once, then use it on a question the same day.

Posterior stores, hypothalamus makes
Oxytocin and ADH are made in the hypothalamus and released from the posterior pituitary.
Use it when: Posterior pituitary hormones.
FLAT PEG
FSH, LH, ACTH, TSH, Prolactin, Endorphin, GH.
Use it when: Anterior pituitary hormones.

Hypothalamus, Pituitary and Hormone Action: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Milk ejection · 1 mark · MCQBoard level

The hormone responsible for milk ejection and uterine contraction during childbirth is:
(a) prolactin
(b) oxytocin
(c) vasopressin
(d) FSH

Try it first, then show the solutionSolution

Oxytocin acts on smooth muscles of the uterus and mammary gland.

Answer: (b) oxytocin

Example 2: Anterior pituitary · 3 marks · Short answerBoard level

Name any four hormones of the anterior pituitary and one function of each.

Try it first, then show the solutionSolution

GH: growth of tissues and bones. (0.75 mark)
Prolactin: development of mammary glands and milk formation. (0.75 mark)
TSH: stimulates the thyroid; ACTH: stimulates the adrenal cortex. (0.75 mark)
LH and FSH: gonadotropins controlling gamete production and sex hormones. (0.75 mark)

Answer: GH, PRL, TSH, ACTH, LH, FSH.

Example 3: Growth hormone disorders · 4 marks · Short answerHarder board level

Distinguish between gigantism, acromegaly and pituitary dwarfism in cause and effect. Why is acromegaly seen only in adults?

Try it first, then show the solutionSolution

Gigantism: excess GH in childhood causes excessive growth of the long bones. (1 mark)
Acromegaly: excess GH in adults enlarges hands, feet and jaw. (1 mark)
Pituitary dwarfism: deficiency of GH in childhood gives short stature with normal proportions. (1 mark)
In adults the growth plates of long bones have closed, so only the bones of the hands, feet and face grow. (1 mark)

Answer: Excess in childhood: gigantism; excess in adults: acromegaly; deficiency: dwarfism.

Example 4: Feedback control · 4 marks · Short answerHarder board level

Explain negative feedback control of thyroid hormone secretion with reference to the hypothalamus and the pituitary. What would be the effect of a thyroid tumour that secretes excess hormone?

Try it first, then show the solutionSolution

The hypothalamus releases TRH, which makes the anterior pituitary release TSH. (1 mark)
TSH stimulates the thyroid to secrete thyroid hormones. (1 mark)
A high level of thyroid hormones inhibits the secretion of TRH and TSH (negative feedback). (1 mark)
With a tumour the level of hormones rises, TSH is suppressed, and the normal thyroid tissue shrinks. (1 mark)

Answer: TRH → TSH → thyroid hormones, which inhibit TRH and TSH.

Example 5: Mechanism of hormone action · 5 marks · Long answerHOTS / competency

Differentiate the action of adrenaline and cortisol at the cellular level. Why does a steroid hormone act more slowly than a peptide hormone? Name the second messenger and an enzyme it activates.

Try it first, then show the solutionSolution

Adrenaline (a catecholamine, an amino acid derivative) is water-soluble, binds a membrane receptor and activates the second messenger cAMP. (1.5 marks)
cAMP activates protein kinase A and enzymes such as the one that breaks down glycogen. (1 mark)
Cortisol (a steroid) crosses the membrane, binds an intracellular receptor and the complex alters gene expression. (1.5 marks)
The steroid action involves transcription and protein synthesis, so it is slower than the immediate enzyme activation by peptide hormones. (1 mark)

Answer: Membrane receptor and cAMP versus intracellular receptor and gene expression.

Where students lose marks in Hypothalamus, Pituitary and Hormone Action

The slips examiners see most often, and what to write instead.

Mistake: Saying the posterior pituitary makes oxytocin
Wrong site.
Do this: It is made in the hypothalamus and stored in the posterior pituitary.
Usually costs: 1 to 2 marks.
Mistake: Confusing gigantism and acromegaly
Reversing age.
Do this: Gigantism in childhood; acromegaly in adults.
Usually costs: 1 mark.
Mistake: Missing negative feedback
Not describing the feedback in the answer.
Do this: High hormone level inhibits the hypothalamus and pituitary.
Usually costs: 1 mark.

Exam tips

Draw a flow chart hypothalamus → pituitary → target gland.
Tabulate hormones, source, target and effect.
State clearly the disorder with the hormone and age.
Describe the two mechanisms of hormone action.

Practice questions on Hypothalamus, Pituitary and Hormone Action

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

Q1 · 1 mark · MCQBoard level
Which hormone regulates the sleep-wake cycle?
(a) melatonin
(b) cortisol
(c) thyroxine
(d) insulin
Hint
Secreted by the pineal gland.
Answer
(a) melatonin
Q2 · 2 marks · Short answerBoard level
What are releasing and inhibiting hormones? Give one example of each.
Hint
Hypothalamic hormones.
Answer
Hormones of the hypothalamus that stimulate (releasing, e.g. GnRH) or inhibit (inhibiting, e.g. somatostatin) the secretion of anterior pituitary hormones.
Q3 · 3 marks · Short answerHarder board level
Why does the posterior pituitary not make its own hormones?
Hint
It stores them.
Answer
Oxytocin and vasopressin are made by neurosecretory cells of the hypothalamus and transported down their axons to the posterior pituitary for storage and release.
Q4 · 3 marks · Short answerHarder board level
Name the disorder caused by deficiency of vasopressin and state its symptom.
Hint
Water loss.
Answer
Diabetes insipidus; large volumes of dilute urine and excessive thirst because the kidneys cannot reabsorb enough water.
Q5 · 3 marks · Assertion-reasonHarder board level
Assertion (A): Peptide hormones act through second messengers. Reason (R): They cannot easily cross the lipid membrane of the target cell. Choose: (a) both true and R explains A (b) both true, R does not explain A (c) A true, R false (d) A false, R true.
Hint
Think about solubility.
Answer
(a) Both true and R explains A.
Q6 · 4 marks · Case-basedHOTS / competency
Case study: Suppose a mother cannot produce enough milk after delivery.
(i) Name the hormone for milk formation. (1 mark)
(ii) Name the hormone for milk ejection. (1 mark)
(iii) Name the gland that stores oxytocin. (1 mark)
(iv) Name the stimulus for its release. (1 mark)
Hint
Prolactin and oxytocin.
Answer
(i) Prolactin. (ii) Oxytocin. (iii) The posterior pituitary (neurohypophysis). (iv) Suckling by the infant.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1.Hormones of the posterior pituitary?Show answer
Oxytocin and vasopressin.
2.Gland that secretes melatonin?Show answer
Pineal.
3.Hormone for milk production?Show answer
Prolactin.
4.Second messenger?Show answer
cAMP.

Hypothalamus, Pituitary and Hormone Action: frequently asked questions

What is the pituitary called?

The master gland, since many of its hormones control other endocrine glands; but it is itself controlled by the hypothalamus.

What are tropic hormones?

Hormones that stimulate other endocrine glands, e.g. TSH and ACTH.

Why are hormones needed in small amounts?

They have high potency and act through amplification systems like cAMP.