What is Gigantism ?
Giagantism is a disease of the hormones or the endocrine glands that makes the affected person like a giant. Over secretion of a hormone causes the overgrowth of the bones of the patient and makes him tall and with broad features.
The hormone implicated in causing gigantism is the growth hormone, which has a normal function in controlling the growth of the body and the bones. The hormone is over secreted if there is a tumor in the brain. The tumor is usually in the area of the brain called as the pitutary gland.
Gigantism is over secretion of growth hormone by a pituitary adenoma before closure of the epiphyses. There is marked increase in height and hypogonadism. Other features resemble acromegaly.
- Enlargement of hands and feet (Spade-like) and tufting of terminal phalanges on X-rays.
- Enlargement of frontal, mastoid and ethmoid sinuses. The calvarium is thickened on X-rays.
- Spine: Kyphoscoliosis, lordosis and osteoporosis.
- Thickening of the clavicles.
- Enlargement of facial bones and prognathism (lantern jaw). Lower incisors may protrude in front of the upper incisors by more than half an inch. The teeth may be spaced apart.
Other organs of the body will be affected due to the over secretion of the growth hormone.
Gigantism Diagnostic Testing
Serum Growth hormone levels.
Plasma insulin-like growth factor 1 (IGF-1), which mediates most effects of growth hormone, is the best diagnostic test. Marked elevations establish the diagnosis.
If IGF-1 levels are only moderately elevated, the diagnosis can be confirmed by giving 75 mg glucose orally and measuring serum growth hormone q30min for 2 hours. Failure to suppress growth hormone to <1 ng/mL confirms the diagnosis of acromegaly. Once the diagnosis is made, the pituitary should be imaged.
If a microadenoma is found on imaging done for another purpose, the patient should be evaluated for clinical evidence of hyperprolactinemia, Cushing’s disease, or acromegaly.
Plasma prolactin should be measured, and tests for acromegaly and Cushing’s syndrome should be performed if symptoms or signs of these disorders are evident.
The treatment of choice is transsphenoidal resection of the pituitary adenoma. Most patients have macroadenomas, and complete tumor resection with cure of gigantism and acromegaly is often impossible. If IGF-1 levels remain elevated after surgery, radiotherapy is used to prevent regrowth of the tumor and to control acromegaly.
Rest of the features of gigantism are very similar to that of Acromegaly. We recommend reading more about Acromegaly on the link below.
Read more about what is acromegaly?