What causes acromegaly?
There are a few different causes of acromegaly. The vast majority are due to a non-cancerous tumor that grows in the pituitary gland of the brain. This tumor causes the pituitary gland to produce too much growth hormone (GH). The high amounts of GH cause the body to release a second hormone called insulin-like growth factor I (IGF-I). The IGF-I causes the excess tissue growth in the body and therefore enlargement of hands, foot, etc. While these tumors in the pituitary gland are not cancerous, if they grow too large the can cause other problems due to compression. These include vision problems or nerve damage. The rate of growth of these tumors vary between people.
The pituitary tumors usually develop randomly and are not due to an underlying genetic cause being passed through the family. Meaning that most cases are not inherited.
Less commonly (less than 5%), acromegaly is not caused by a pituitary tumor. Instead it is caused by a tumor in the lung, pancreas or other area of the brain. Usually, these tumors produce too much growth hormone-releasing hormone (GHRH). In turn, this hormone triggers the pituitary gland to release GH. The end result for the body is the same, but the cause is elsewhere. When the non-pituitary tumor is removed, the GH level falls and the symptoms of acromegaly improve. It is important to note patients with non-pituitary tumors can still have an enlarged pituitary (due to excess GH production). So it is important to not assume the tumor is in the pituitary gland to account for these rare possibilities.
"Acromegaly" National Institute of Diabetes and Digestive and Kidney Diseases. April 2012. https://www.niddk.nih.gov/health-information/health-topics/endocrine/acromegaly/Pages/fact-sheet.aspx#common