Pineal physiology and pathophysiology, including pineal tumours
- DOI:
- 10.1093/med/9780199235292.003.2222
The pineal gland is innervated mainly by sympathetic nerve fibres that inform the gland of the prevailing light-dark cycle and acts as a neuroendocrine transducer. The gland is located behind the third ventricle in the centre of the brain and is a highly vascular organ formed by neuroglial cells and parenchymal cells or pinealocytes. The latter synthesize melatonin as well as other indoleamines and peptides.
The main pineal hormone melatonin (N-acetyl-5-methoxytryp-tamine) exhibits an endogenous circadian rhythm, reflecting signals originating in the suprachiasmatic nucleus; environmental lighting entrains the rhythm, by altering its timing. Independently of sleep, pineal melatonin is inhibited by light and stimulated during darkness, thanks to the neural input by a multisynaptic pathway that connects the retina, through the suprachiasmatic nucleus of the hypothalamus, preganglionic neurons in the upper thoracic spinal cord and postganglionic sympathetic fibres from the superior cervical ganglia, with the pineal gland.
Melatonin deficiency may produce sleeping disorders, behavioural problems, or be associated with precocious or delayed puberty in children, while chronically elevated melatonin has been observed in some cases of hypogonadotropic hypogonadism (1, 2).
Access to the complete content on Oxford Medicine Online requires a subscription or purchase. Public users are able to search the site and view the abstracts for each book and chapter without a subscription.
Please subscribe or login to access full text content.
If you have purchased a print title that contains an access token, please see the token for information about how to register your code.
For questions on access or troubleshooting, please check our FAQs, and if you can't find the answer there, please contact us.
