Definition
Primary hyperparathyroidism causes hypercalcemia (elevated blood calcium levels) through the excessive secretion of parathyroid hormone (PTH), usually by an adenoma of the parathyroid glands.
Symptoms
The signs and symptoms of primary hyperparathyroidism are those of hypercalcemia:
- kidney stones
- nephrocalcinosis
- diabetes insipidus (polyuria and polydipsia)
- bone-related complications
- The classic bone disease in hyperparathyroidism is osteitis fibrosa cystica, which results in pain and sometimes pathological fractures. Other bone diseases associated with hyperparathyroidism are osteoporosis, osteomalacia, and arthritis.
- gastrointestinal symptoms of constipation, indigestion, nausea and vomiting. Hypercalcemia can lead to peptic ulcers and acute pancreatitis
- effects on the central nervous system. Symptoms include lethargy, fatigue, depression, memory loss, psychosis, ataxia, delirium, and coma
- Left ventricular hypertrophy
Other signs include proximal muscle weakness, itching, and band keratopathy of the eyes.
Causes
The most common cause of primary hyperparathyroidism is a sporadic, single parathyroid adenoma resulting from a clonal mutation (~97%).
Less common are
- hyperplasia of all parathyroid glands (~2.5%),
- parathyroid carcinoma (malignant tumor),
- adenomas in more than one gland (together ~0.5%).
Primary hyperparathyroidism is also a feature of several familial endocrine disorders
A deficiency of vitamin D has also been associated with a more severe condition of patients affected by primary hyperparathyroidism.
Diagnosis
The diagnosis of primary hyperparathyroidism is made by blood tests. Serum calcium levels are elevated.
The serum chloride phosphate ratio is 33 or more in most patients with primary hyperparathyroidism. However, thiazide medications have been reported to causes ratios above 33.
Urinary cAMP is occasionally measured; this is generally elevated.
Intact PTH levels are also elevated.
In all cases, the disease is idiopathic, but is thought to involve inactivation of tumor suppression genes, or involve gain of function mutations.
Treatment
Treatment is usually surgical removal of the gland(s) containing adenomas.
Medications include estrogen replacement therapy in postmenopausal women and bisphosphonates.
Newer medications termed "calcimimetics" used in secondary hyperparathyroidism are now being used in Primary hyperparathyroidism. Their benefits are as yet unclear.
