Growth hormone (GH) is produced by the pituitary gland. It stimulates the growth of muscle, cartilage and bone.

In rare circumstances, the pituitary gland produces excessive amounts of GH. Invariably this is the result of a pituitary tumour, which in most cases is non-cancerous.

Occasionally, the tumour appears as part of an inherited condition called multiple endocrine neoplasia. In most cases, however, why the tumour occurs remains a mystery.

As the pituitary gland is located just below the brain, as the tumour grows it may press on the brain, causing headaches. It may also affect vision, usually noticed as a reduction in a person's field of vision.

It's most common for pituitary tumours to occur in adulthood. Although the long bones of the arms and the legs are no longer capable of growing, the bones of the hands, feet, and face can still grow, and do so.

When excessive growth hormone is present before puberty, it causes rampant growth, or gigantism.

Acromegaly causes the hands to become spade-like in appearance. Growth of the facial bones causes the face to change shape too. The jaw becomes larger, with spaces appearing between the teeth, and the eyebrows become more prominent. The tongue enlarges and the skin becomes coarse and oily.

Non-bony parts of the body (soft tissue) may also grow larger, leading to weight gain and thickening of the skin. Other characteristic changes include deepening of the voice, excess sweating, and numbness and tingling in the hands and feet. Enlargement takes place over years and may only be noticed when old photographs are compared with recent ones or when larger shoes are needed.

Acromegaly can have serious effects on the body. If not treated, diabetes and chronic heart failure may occur.

Once the diagnosis has been confirmed by blood tests and scans, treatment can be provided. This may include a combination of surgery to remove the tumour, radiotherapy to destroy any tumour cells and drugs to suppress the production of GH.

Regular follow-up monitoring is provided. In time, although the bones will remain the same size, any soft tissues that have enlarged will become smaller.

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