Causes
Acromegaly is usually caused by a pituitary macroadenoma (more than 1cm diameter). Rarely, it can be caused by autonomous GH secretion by an ectopic tumor.
Clinical suspicion
Pituitary macroadenomas can lead to the development of pressure manifestations including deep seated bitemporal headaches or occipital headaches in cases with increased intracranial tension. Cranial nerve affection may include bitemporal hemianopsia in addition to occular nerve or trigeminal never affection. Brain stem affection can lead to quadriparesis with upper motor neuron signs.
Acromegaly is suspected on clinical examination based on the presence of characteristic manifestations. These include acromegalic facies (with elongated face, prominent orbital ridges, large nose, prominent lower jaw and thickening of the lips), thick skin, enlargement of the hand (spade like hands) and foot, visceromegaly and macroglossia, carpal tunnel syndrome, dorsal kyphosis, hypertension and cardiomyopathy in addition to an increased incidence of ischemic heart disease.
Endocrinal manifestations include impaired glucose tolerance, diabetes (20%), galactorrhoea, menstrual irregularities, loss of libido and in some cases gonadal atrophy.
Diagnosis
Acromegaly is sometimes very difficult to diagnose as the manifestations may evolve very gradually. Once suspected diagnostic investigations include glucose tolerance test and insulin-like growth factor-1 (IGF-1, somatomedin C) assays.
- Glucose tolerance test: Normally growth hormone is suppressed after oral intake of 50mg of glucose due to inhibition of GHRH secretion. In cases of acromegaly growth hormone levels fail to suppress or may even rise.
- Insulin-like growth factor-1 (IGF-1, somatomedin C) assays are always elevated in acromegaly and do not fluctuate like growth hormone levels.
Treatment
Treatment is mainly surgical using transfenoidal adenectomy or hypophysectomy of the acidophil adenoma. This is the treatment of choice especially if the case is urgent and accompanied by complications such as visual field defects.
Bromocriptine paradoxically leads to a significant reduction in growth hormone levels. Cabergonline is another dopaminergic agonist used to reduce growth hormone levels in gigantism.
Octreotide is a synthetic somatostatin analogue which is more effective than bromocryptine.
External radiotherapy is an option in treating acidophil adenomas when other options have failed or are inappropriate. Hypopituitarism can occur in 20% of cases.
