Clinical Manifestations Of Primary Hyperparathyroidism As a Major Disorder Of Parathyroid Glands
Causes Of Hyperparathyroidism
When pathological hypersecretion of PTH occurs persistently, it results in hyperparathyroidism. It is characterized by hypercalcemia, hypophosphatemia, metabolic bone disease, recurrent nephrolithiasis, renal damage, peptic ulceration and other complications. Adult women are more affected than men. A wide spectrum of severity ranging from an asymptomatic illness of fatal hypercalcemic crisis is seen.
- Benign adenoma of one parathyroid gland,
- Hyperplasia of all the parathyroid glands, or
In 80% of cases, the lesion is an adenoma which may vary from 0.5 to 5g. Histologically, the adenoma is composed of chief cells in the vast majority, but at times oxyphil cells or mixed cells may predominate. Adenomas remain well-encapsulated within a rim of normal tissue. Ectopic foci for parathyroid adenomas include thymus, thyroid pericardium or retro-esophageal space. About 15% of cases are due to diffuse or nodular hyperplasia affecting all or most of the parathyroid glands. Carcinoma is rare. When present, it affects only gland. The degree of malignancy is low. Adenoma or carcinoma may be part of the multiple endocrine neoplasia syndromes. MEN-1 (pituitary and pancrease) or MEN-II (medullary carcinoma or thyroid and adrenal pheochromocytomas).
The presenting symptoms may vary depending on hypercalcemia, renal involvement, bone involvement or other complications. Sometimes a tumour may be palpable in the neck or visualized radiologically in the mediastinum.
Hypercalcemia: Hypercalcemia manifests in several ways. Common symptoms include lethargy, polyuria, polydipsia, drowsiness, confusion, weight loss, generalized muscle weakness, hypertension and autonomic dysfunction such as anorexia, uncontrolled vomiting and constipation. Proximal muscle weakness may be prominent. Severe cases go into stupor and coma. Longstanding hypercalcemia leads to metastatic calcification in the lings, cornea, kidneys, blood vessels and other organs. The corneal lesion is band keratopathy in which calcium deposition is best demonstrated by slit lamp examination. Cardiac dysfunction occurs. Ventricular systole is shortened. Electrocardiogram shows shortened QT interval and other nonspecific changes.
Renal manifestations: Nephrolithiasis, nephrocalcinosis and disorders of glomerulo-tubular functions are common in longstanding cases. Renal calculi are made up of a mixture of calcium oxalate and calcium phosphate. Renal stones tend to be recurrent. Hypercalcemia predisposes to urinary infection. Nephrocalcinosis is usually associated with bony changes such as osteitis fibrosa cystic. Glomerular filtration rate is reduced. Blood urea and serum creatinine are elevated. Tubular dysfunction also occurs. Correction of hypercalcemia reverses the functional defects in the kidneys.
Alimentary manifestations: Hypercalcemia increases gastric production and thus predisposes to peptic ulceration. Zollinger- Ellison syndrome may coexist (multiple endocrine neoplasia type I). Hypercalcemia leads to chronic pancreatitis, pancreatic calcification or acute hemorrhagic pancreatitis.
Skeletal manifestations: Osteitis fibrosa cystic or diffuse loss of bone tissue such as osteoporosis or osteomalacia may occur. Osteitis fibrosa cystic is accompanied by severe localized bone pain, marked deformities and pathological fractures. In osteitis fibrosa, the bone trabeculae are reduced. There is increase in multinucleated osteoclasts and fibrovascular tissue. Radiological abnormalities of bone include subperiosteal erosion of cortical bone, demineralization, local destructive lesions, cystic changes- (bone cysts and brown tumours) and calcification of fibrocartilage. The phalanges show loss of bone tuft and subperiosteal erosions, and these are diagnostic. Acromioclavicular jonts, symphysis pubis and sacroiliac joints also show similar changes.
Osteopenia is seen characteristically as punched out and mottled areas in the skull (pepper pot skull). The lamina dura of the teeth is lost. With successful treatment of hyperparathyroidism all the radiological abnormalities clear up. Joints may show chondrocalcinosis and degenerative changes.
© 2014 Funom Theophilus Makama