Pituitary Histology

Prepared and reviewed by the PrepElephant Academic Review Team

First published 2 Oct 2026 · Spot an error?

On this page

Direct answer
What you must remember
Reading the slide under two different laws
Where students slip
Frequently asked questions
Related topics

Direct answer

Rathke's pouch, an upward outpouching of the primitive oral cavity, meets the infundibulum, a downward extension of the hypothalamus, to build the two lobes of the hypophysis — and their histologies could not be more different. The adenohypophysis (pars distalis, pars tuberalis, pars intermedia) is glandular epithelium of chromophils and chromophobes: acidophils stain red-orange and secrete growth hormone and prolactin, while basophils stain blue-purple with haematoxylin or PAS and secrete ACTH, TSH, LH and FSH. The neurohypophysis (pars nervosa plus infundibular stalk) is not epithelium at all but a bed of unmyelinated axons descending from the supraoptic and paraventricular nuclei, supported by pituicytes and studded with Herring bodies — the neurosecretory granule swellings that store antidiuretic hormone and oxytocin until release into capillaries.

What you must remember

Acidophils: somatotrophs (growth hormone — the commonest cell type) and lactotrophs (prolactin, which enlarges in pregnancy); orange-red with orange-G or eosin.
Basophils: corticotrophs (ACTH), thyrotrophs (TSH) and gonadotrophs (LH, FSH); PAS-positive because their glycoprotein hormones carry carbohydrate residues.
Chromophobes: poorly staining cells, either degranulated chromophils or reserve stem cells — not a separate hormone line.
Pars intermedia: a thin, rudimentary strip in humans with colloid-filled cysts — Rathke pouch remnants; its craniopharyngioma (adamantinomatous) counterpart arises from squamous rests along the pouch track.
Neurohypophysis: axons from supraoptic (chiefly antidiuretic hormone) and paraventricular (chiefly oxytocin) nuclei, with pituicytes as the glial support and Herring bodies as the storage swellings.
Hormone-making rule: adenohypophysis synthesises its hormones de novo; neurohypophysis only stores and releases hypothalamic products — the most-asked distinction.
Clinical anchors: growth-hormone-secreting acidophil adenoma before epiphyseal fusion causes gigantism and after fusion acromegaly; prolactinoma is the commonest functioning adenoma, with amenorrhoea and galactorrhoea.
Staining hierarchy: routine H and E separates acidophils and basophils; specific stains or immunohistochemistry identify individual cell types.

Reading the slide under two different laws

On an H and E section of the whole gland, the anterior lobe looks like a solid epithelial organ: cords and nests of cells wrapped by rich sinusoidal capillaries, mixing orange-pink acidophils, purple basophils and pale chromophobes. Scan across to the posterior lobe and the character changes abruptly — pale, fibrillar, nerve-like tissue in which only the nuclei of pituicytes and a few capillaries interrupt the axonal mat. That abrupt transition is the embryology showing: mesodermal competence meets neuroectoderm across a slit-like pars intermedia, often marked by colloid cysts left over from Rathke's pouch.

Each cell type can then be tied to its axis and its tumour. Somatotroph excess before puberty closes the epiphyses and produces the gigantism of examiners' lore; after closure the same adenoma enlarges jaw, hands and feet as acromegaly, and histology shows a monomorphous field of acidophils or sparsely granulated chromophobes. Corticotroph hyperplasia or adenoma drives Cushing disease, while craniopharyngioma — histologically palm-like squamous rests and wet keratin — grows along the Rathke track above the sella, compressing the optic chiasma in a child or adolescent with headache and bitemporal field loss. Reading the slide with these laws in mind converts a confusing mosaic into a map.

Where students slip

The slip that costs most marks is treating the posterior pituitary as a hormone-synthesising gland: it makes nothing, and diabetes insipidus follows damage to the hypothalamic nuclei or their tract, classically after head injury or surgery near the pituitary — the hormone is merely warehoused in Herring bodies downstream. A second confusion is basophil versus acidophil memory: pair the chemistry with the charge — glycoprotein hormones (TSH, LH, FSH) and the POMC-derived ACTH are basophilic and PAS-positive, while the plain protein hormones growth hormone and prolactin are acidophilic. Finally, examiners ask why chromophobes stain faintly; the safe answer is degranulation after active secretion plus a reserve population, and many clinically functioning adenomas are chromophobe on routine stains — a viva favourite precisely because it tests understanding over rote colour-matching.

Frequently asked questions

Which hormones come from acidophils of the anterior pituitary?

Growth hormone from somatotrophs and prolactin from lactotrophs — both plain proteins that stain with acid dyes.

What are Herring bodies?

Dilated axon terminals in the neurohypophysis packed with neurosecretory granules of antidiuretic hormone and oxytocin awaiting release into capillaries.

Why does the neurohypophysis not synthesise hormones?

It is composed of axons from the supraoptic and paraventricular nuclei; the hormones are made in hypothalamic cell bodies and only stored and released in the posterior lobe.

What is the embryological origin of craniopharyngioma?

Squamous epithelial rests of the Rathke pouch tract — the same oral ectoderm that forms the adenohypophysis.

Which pituitary cell type enlarges during pregnancy?

Lactotrophs, which proliferate and enlarge the anterior lobe markedly — one reason prolactinoma diagnosis and surgery in pregnancy demand care.