What does the pineal gland do? why might it need to be removed?

Pineal function: The pineal gland makes melatonin. Although the exact function and significance is not fully know, it probably plays a role in circadian rhythm (sleep) and may be involved in reproductive function. It is common for the pineal to calcify, and then is shows up on xrays/scans. The calcification is not a problem. Tumors can form in the pineal, but they are rare (that would be a reason to remove).