Pineal Gland

Anatomy

• Small endocrine gland located in epithalamus, near center of 🧠 betn the 2 hemispheres.
• Attached to roof of 3rd ventricle.
• Not protected by blood-🧠 barrier — exposed to systemic circulation.
• Innervated by postganglionic sympathetic fibers from superior cervical ganglion.

Physiology & Func

• Main func: Secretion of melatonin — hormone regulating sleep-wake (circadian) cycle.
• Melatonin production is stimulated by darkness & inhibited by light.
• Melatonin acts on suprachiasmatic nucleus (SCN) of hypothalamus to regulate circ rhythms.

Clinical Relevance

• Pinealoma: Tumor of pineal gland. May compress vertical gaze center (superior colliculus).
• Parinaud Syndrome: Due to pinealoma → upward gaze palsy, light-near dissociation, convergence-retraction nystagmus.
• Precocious puberty: Seen in children w pineal tumors due to decreased melatonin inhibition on GnRH.
• Sleep disorders: Disrupted melatonin rhythm seen in insomnia, jet lag, shift work disorder.
• Calcification: Pineal gland often calcifies w age — normal on CT scan in adults.

Imaging

• Calcified in most adults — visible on CT (often used as midline marker).
• Lesions like pinealoma visible on MRI (midline mass posterior to 3rd ventricle).

Summary

Feature	Details
Location	Midline, posterior to 3rd ventricle, part of epithalamus
Main Hormone	Melatonin
Func	Regulates circ rhythm
Stimulated by	Darkness
Clinical Disorders	Parinaud syndrome, precocious puberty, pinealoma

Pineal Gland Flashcards

Where is it located?

Posterior to 3rd ventricle, in epithalamus, near superior colliculi.

What hormone does it produce?

Melatonin.

What stimulates melatonin release?

Darkness (inhibition by light via retinal input to hypothalamus).

What are the symps of Parinaud syndrome?

Upward gaze palsy, light-near dissociation, convergence-retraction nystagmus.

What type of tumor can cause Parinaud syndrome?

Pinealoma compressing superior colliculi.

Why can a pinealoma lead to early puberty?

Loss of melatonin inhibition → ↑ GnRH release → precocious puberty.

How does pineal gland appear on imaging in adults?

Calcified on CT — normal finding with age.

What is the function of melatonin?

Regulates circadian rhythm and promotes sleep.