The most common cause is prolonged hypersecretion of growth hormone(GH),usually by a hormone-secreting pituitary tumour. The conditions are only occasionally due to excess growth hormone releasing hormone(GHRH) secreted by the hypothalamus. As the tumour increases in size,compression of nearby structures may lead to:
- Hyposecretion of other pituitary hormones of both the anterior and posterior lobes.
- Damage to the optic nerves,causing visual disturbances.
The effects of excess GH include:
- Excessive growth of bones.
- Enlargement of internal organs.
- Formation of excess connective tissue.
- Enlargement of the heart and raised blood pressure.
- Reduced glucose tolerance and a predisposition to diabetes mellitus.
GIGANTISM.
This occurs in children when there is excess GH while epiphyseal cartilages of long bones is complete. It is evident mainly in the bones of the limbs,and affected individuals may grow to heights of 2.1 to 2.4 m,although body proportions remain normal.
ACROMEGALY.
This means ‘large extremities’ and occurs in adults when there is excess GH after ossification is complete. The bones become abnormally thick and there is thickening of soft tissues. These changes are most noticeable as coarse facial features ( especially excessive growth of the lower jaw),an enlarged tongue and excessively large hands and feet.
