acromegaly
Meaning of acromegaly: Changes arrive so slowly that old photographs, a ring that no longer fits or a rising shoe size often reveal them first.
Definition of acromegaly
Acromegaly is the condition produced by too much growth hormone in an adult, after the growth plates in the long bones have closed. Bones can no longer lengthen, so they thicken instead, and the soft tissue over them enlarges as well. Hands, feet and facial bones change most visibly. The excess almost always comes from a benign tumor of the pituitary gland.
How does the hormone cause the changes?
Growth hormone works mostly at second hand. It travels to the liver and prompts release of insulin-like growth factor 1, which is the molecule that actually drives tissue growth. In childhood that lengthens bone at the growth plates. Once those plates fuse, the same signal can only add width, so bone thickens at the brow, jaw, hands and feet, and cartilage, skin and internal organs enlarge alongside. Timing is the whole distinction between two conditions with one cause.
| Gigantism | Acromegaly | |
|---|---|---|
| When the excess starts | Before growth plates close | After they close |
| Main effect | Great height | Thickening and enlargement, height unchanged |
What does it do beyond appearance?
The visible changes are the least of it. Swollen soft tissue in the wrist compresses the median nerve, producing carpal tunnel symptoms. Cartilage overgrowth damages joints and causes lasting pain. Tissue in the upper airway narrows it, so obstructive sleep apnea is common. The heart muscle thickens, blood pressure rises, and the same hormone opposes insulin, so blood sugar rises too. The tumor itself can press upward on the crossing point of the optic nerves, cutting the outer field of vision on both sides, and sideways on the rest of the pituitary gland, reducing other hormones.
How is it identified?
A single growth hormone measurement is close to useless, because the gland releases it in pulses and a level can be high or low within the same hour for entirely normal reasons. Insulin-like growth factor 1 is measured instead, since it stays steady through the day and reflects the average exposure. A confirmatory test gives a sugary drink, which in health suppresses growth hormone sharply and fails to do so in acromegaly. Imaging of the pituitary then locates the tumor.
Used in a sentence
Imaging identified a pituitary tumor consistent with the patient's diagnosis of acromegaly.
Good to know
Acromegaly develops gradually over years, so the physical changes are often unnoticed by the person and those around them until a comparison with older photographs or a change in ring or shoe size prompts evaluation.
Word origin
Where “acromegaly” comes from
Formed from Greek akron, meaning extremity, and megas, meaning large, describing the enlargement of the hands, feet and facial bones.