Pineal gland and the diffuse endocrine system !
- Organ
The pineal makes melatonin, which sets the day-night rhythm; many other hormone cells are spread through other organs.
Updated 2026-11-01
See it in 3D: Pineal gland
What it is
The pineal is a small gland on the roof of the third ventricle, made of pinealocytes and glial cells. It makes melatonin from serotonin, mostly in darkness. Outside the classic glands, single endocrine cells sit in the gut, lung, heart and kidney: the diffuse endocrine system. Their tumours are the neuroendocrine tumours, such as carcinoid.
Structure
- Pineal on H&E: lobules of pale pinealocytes separated by septa, with astrocytes and layered basophilic calcified concretions.
- Enteroendocrine cells: single cells at the base of intestinal glands, with granules facing the basement membrane (they secrete into the blood).
- Pulmonary neuroendocrine cells: single or in neuroepithelial bodies in the bronchial epithelium.
Function
- Melatonin sets the circadian sleep rhythm; high levels in childhood may hold back puberty.
- Diffuse endocrine cells regulate local tasks: digestion (gastrin, secretin, cholecystokinin), pressure (atrial natriuretic peptide) and red cells (erythropoietin).
Where the diffuse endocrine system lives
| Site | Cell | Hormone | Correlation |
|---|---|---|---|
| Pineal | Pinealocyte | Melatonin | Jet lag, pineal tumours |
| Gut and stomach | Enteroendocrine cells | Serotonin, gastrin, secretin, cholecystokinin, GLP-1 | Carcinoid tumour and carcinoid syndrome |
| Lung | Pulmonary neuroendocrine cells | Peptides and amines | Bronchial carcinoid and small cell carcinoma |
| Heart | Atrial myocytes | Atrial natriuretic peptide | Rises in heart failure (BNP from the ventricle) |
| Kidney | Interstitial and juxtaglomerular cells | Erythropoietin and renin | Anemia of chronic kidney disease |
Markers
- Chromogranin A
- Synaptophysin
- Ki-67 (grade of neuroendocrine tumours)
Clinical notes
- Germ cell tumours of the pineal region: more common in young males.
- Small cell lung carcinoma is neuroendocrine and can make ACTH or ADH ectopically.
Test yourself
Think of the answer, then tap the question to see it.
Which hormone does the pineal make and what inhibits it?
Melatonin; light reaching the retina inhibits it, through the suprachiasmatic nucleus.
What are corpora arenacea (brain sand)?
Layered calcified concretions inside the pineal that increase with age and show on imaging.
Which markers identify neuroendocrine cells and tumours?
Chromogranin A and synaptophysin.
See it in 3D
The structures of Durgical's 3D anatomy where it is found.
Related
- Enteroendocrine cells and GALT
- Islets of Langerhans: α, β, δ cells
- Adrenal cortex zones and medulla
- Pituitary: adenohypophysis and neurohypophysis
Related conditions
Educational content on normal microscopic structure and its clinical relevance; no substitute for studying slides or for a health professional's advice.
Sources: 17.7 The Pineal Gland (OpenStax, Rice University, 2022); Pituitary & Pineal Glands (National Cancer Institute, SEER Training Modules, 2026); 17.10 Organs with Secondary Endocrine Functions (OpenStax, Rice University, 2022).
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Representative model, for educational purposes only.