|Classification and external resources|
Thyroid and parathyroid.
Primary hyperparathyroidism causes hypercalcemia (elevated blood calcium levels) through the excessive secretion of parathyroid hormone (PTH), usually by an adenoma (benign tumors) of the parathyroid glands. It is the most common cause of elevated calcium levels. The symptoms of the condition relate to the elevated calcium levels, which can cause digestive symptoms, kidney stones, mental features and bone disease.
The diagnosis is initially made on blood tests; an elevated level of calcium together with a raised level of parathyroid hormone are typically found. To identify the source of the excessive hormone secretion, medical imaging may be performed. Parathyroidectomy, the surgical removal of one or more parathyroid glands, may be required to control symptoms.
Signs and Symptoms
The signs and symptoms of primary hyperparathyroidism are those of hypercalcemia. They are classically summarized by the mnemonic "stones, bones, abdominal groans, thrones and psychiatric moans".
- "Stones" refers to kidney stones, nephrocalcinosis, and diabetes insipidus (polyuria and polydipsia). These can ultimately lead to renal failure.
- "Bones" refers to 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.
- "Abdominal groans" refers to gastrointestinal symptoms of constipation, indigestion, nausea and vomiting. Hypercalcemia can lead to peptic ulcers and acute pancreatitis. The peptic ulcers can be an effect of increased gastric acid secretion by hypercalcemia.
- "Psychiatric moans" refers to effects on the central nervous system. Symptoms include lethargy, fatigue, depression, memory loss, psychosis, ataxia, delirium, and coma.
- "Thrones" refers to polyuria and constipation
- Left ventricular hypertrophy.
Other signs include proximal muscle weakness, itching, and band keratopathy of the eyes.
When subjected to formal research, symptoms of depression, pain, and gastric dysfunction seem to correlate with mild cases of hypercalcemia.
The diagnosis of primary hyperparathyroidism is made by blood tests.
Serum calcium levels are elevated, and the parathyroid hormone level is abnormally high compared with an expected low level in response to the high calcium. A relatively elevated parathyroid hormone has been estimated to have a sensitivity of 60%-80% and a specificity of approximately 90% for primary hyperparathyroidism.
A more powerful variant of comparing the balance between calcium and parathyroid hormone is to perform a 3 hour calcium infusion. After infusion, a parathyroid hormone level above a cutoff of 14 ng/l has a sensitivity of 100% and a specificity of 93% in detecting primary hyperparathyroidism, with a confidence interval of 80% to 100%.
The serum chloride/phosphate ratio is 33 or more in most patients with primary hyperparathyroidism. However, usage of thiazide medications have been reported to causes ratios above 33. Studies without any usage of thiazide diuretics have estimated a serum chloride/phosphate ratio to have a sensitivity of 94% or 95% and a specificity of 96% or 100%.
Urinary cAMP is occasionally measured; this is generally elevated.
Parathyroid hormone activity
Intact PTH levels are also elevated.
The most common cause of primary hyperparathyroidism is a sporadic, single parathyroid adenoma resulting from a clonal mutation (~97%). Less common are parathyroid hyperplasia (~2.5%), parathyroid carcinoma (malignant tumor), and adenomas in more than one gland (together ~0.5%).
Genetic associations include:
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Primary hyperparathyroidism can also result from pregnancy. It is apparently very rare, with only about 110 cases have so far been reported in world literature, but this is probably a considerable underestimate of its actual prevalence in pregnant women.
Treatment is usually surgical removal of the gland(s) containing adenomas, but medication may also be required.
The surgery on parathyroid is called "Parathyroidectomy"; it was first done in 1925. The symptoms of the disease, listed above, are indications for surgery. Surgery reduces all cause mortality as well as resolving symptoms. However, cardiovascular mortality is not significantly reduced.
A consensus statement in 2002 recommended the following indications for surgery in asymptomatic hyperparathyroidism:
- Serum calcium: 1.0 mg/dl above upper limit of normal
- 24-h urinary calcium >400 mg
- Creatinine clearance reduced by 30% compared with age-matched subjects.
- Bone mineral density t-score <−2.5 at any site
- Age <50
More recently, three randomized controlled trials have studied the role of surgery in patients with asymptomatic hyperparathyroidism. The largest study reported that surgery showed increase in bone mass, but no improvement in quality of life after one to two years among patients with:
- Untreated, asymptomatic primary hyperparathyroidism
- Serum calcium between 2.60–2.85 mmol/liter (10.4–11.4 mg/dl)
- Age between 50 and 80 yr
- No medications interfering with Ca metabolism
- No hyperparathyroid bone disease
- No previous operation in the neck
- Creatinine level < 130 µmol/liter (<1.47 mg/dl)
Newer medications termed "calcimimetics" used in secondary hyperparathyroidism are now being used in primary hyperparathyroidism. Calcimimetics reduce the amount of parathyroid hormone released by the parathyroid glands. They are recommended in patients in whom surgery is inappropriate.
The incidence of primary hyperparathyroidism is approximately 1 per 1,000 people (0.1%), while there are 25-30 new cases per 100,000 people per year in the United States. The prevalence of primary hyperparathyroidism has been estimated to be 3 in 1000 in the general population and as high as 21 in 1000 in postmenopausal women. It is almost exactly three times as common in women as men.
Primary hyperparathyroidism is associated with increased all-cause mortality.
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- Description of primary hyperparathyroidism with graphical statistics at Parathyroid.com