Significant Clinical Manifestations Of Pituitary Hyperfunction Disorders: Acromegaly And Gigantism
Gigantism And Acromegaly
Effects of excessive amounts of growth hormone (GH) depend on the age of onset of the disease. Onset before closure of the epiphyses leads to gigantism and late onset after closure of epiphyses results in acromegaly.
Causes: Hyperplasia or adenoma of the pituitary affecting the acidophils, chromophobes or both leads to hypersecretion of GH. The total clinical picture results from the physical effects of the tumour and endocrine effects of GH. The tumour compresses the neighbouring cells in the pituitary and leads to suppression of gonadotrophs and thyrotrophs. Mixed acidophil adenoma produces both GH and PRL. Larged-sized tumours may cause rise in intracranial tension.
This is usually seen before the age of 10 years. This disorder is caused in majority of cases by hyperplasia of the eosinophilic cells of the pituitary. There is disproportionate growth in height and size. Maximal linear growth occurs in the bones of the extremities so that the arm span exceeds the height and the lower segment exceeds the upper. Early stages of the disease include muscular hypertrohly and sexual precocity. Later, features of acromegaly may also develop.
This is seen in adults, between the ages of 20-50. Both sexes are affected.
Clinical features: The onset is insidious. There is increase in soft tissues and bones of the hands, feet and skull. The face is elongated and the features are coarse. Lips, tongue, nose, salivary glands and lacrimal glands are enlarged. The mandible is prominent and prognathic. Growth of the mandible leads to separation of the lower incisors. The larynx is enlarged and the voice becomes husky. Thyroid may enlarge under the influence of GH, but there is no hyperfunction. During the active stage, excessive sweating occurs. Spine may show kyphosis, enlargement of vertebrae and osteoarthrosis. Arthritis with hypertrophy and edema of periarticular tissues may occur in the peripheral joints. Bony prominences and attachments of muscles to bone become hypertrophied. Though the bones increase in thickness, unlike in gigantism, the length does not increase. There is generalized enlargement of all viscera. The changes in the heart include enlargement, specific cardiomyopathy and congestive cardiac failure. The nerves are thickened which may lead to entrapment neuropathies such as carpal tunnel syndrome. Increase in collagen fibers in the nerves may result in peripheral neuropathy. Though the muscles are hypertrophied, they may be weak due to proximal myopathy. Glucose intolerance develops in 25- 30% of cases and many proceed to overt diabetes mellitus. Males complain of loss of libido. Females develop amenorrhea. Gynecomastia and galactorrhea may be seen in some cases.
Diagnosis And Treatment
Course and prognosis: The endocrine disturbances and local pressure effects progress in cases with pituitary tumours. Death occurs due to increased intracranial tension, diabetic complications, cardiac failure or infections. The course depends on the nature of the pituitary tumour and its growth. In many cases, the condition may be arrested spontaneously.
Diagnosis: Acromegaly should be suspected clinically from the appearances of the patient. The diagnosis has to be established by investigations.
- Radiology: X-ray of skull reveals enlargement of the sella turcica. Prominence of the bony points of the skull and enlargement of the frontal air sinuses are suggestive points. X-ray of chest may reveal cardiomegaly. Hands and feet show tufting of the phalanges and enlargement of soft tissues.
- GH estimation: Basal GH levels in blood are elevated. The diagnostic finding is the failure of suppression of GH levels by a glucose load. Other pituitary hormones also may show alteration.
- Biochemical tests: Suggestive but non-specific tests include impaired glucose tolerance in many cases and elevation of serum calcium and phosphate in 10-20%.
- Surgery: This is the method of choice if there are no contraindications. Impairment of vision is an indication for urgent surgery. The GH levels fall rapidly after surgery.
- Irradiation: The pituitary can be irradiated by implantation of radon seeds or yttrium. Alpha particles and protons have been introduced for this purpose recently.
Finally, in cases where surgery is contraindicated, bromocriptine which is an ergot derivative is used. This drug reduced GH levels consistently in 50% of cases. Medication has to be continued in a dose of up to 10mg/day for several months. The physical abnormalities regress with successful therapy. Though the diabetic state may improve in many cases, it may persis in some. Total blindness may not recover. Complications like cardiomyopathy, diabetes mellitus, and neuropathy can be avoided by early treatment.
© 2014 Funom Theophilus Makama