Hypoparathyroidism is decreased function of the parathyroid glands with underproduction of parathyroid hormone (PTH). This can lead to low levels of calcium in the blood, often causing cramping and twitching of muscles or tetany (involuntary muscle contraction), and several other symptoms. It is a very rare disease. The condition can be inherited, but it is also encountered after thyroid or parathyroid gland surgery, and it can be caused by immune system-related damage as well as several rarer causes. The diagnosis is made with blood tests, and other investigations such as genetic testing, depending on the results. The primary treatment of hypoparathyroidism is calcium and vitamin D supplementation. Calcium replacement or vitamin D can ameliorate the symptoms but can increase the risk of kidney stones and chronic kidney disease.
Signs and symptoms
The main symptoms of hypoparathyroidism are the result of the low blood calcium level, which interferes with normal muscle contraction and nerve conduction. As a result, people with hypoparathyroidism can experience paresthesia, an unpleasant tingling sensation around the mouth and in the hands and feet, as well as muscle cramps and severe spasms known as "tetany" that affect the hands and feet. Many also report a number of subjective symptoms such as fatigue, headaches, bone pain and insomnia. Crampy abdominal pain may occur. Physical examination of someone with hypocalcemia may show tetany, but it is also possible to provoke tetany of the facial muscles by tapping on the facial nerve (a phenomenon known as Chvostek's sign) or by using the cuff of a sphygmomanometer to temporarily obstruct the blood flow to the arm (a phenomenon known as Trousseau's sign of latent tetany). Chronic hypoparathyroidism results in persistent low calcium with high phosphate in the body, which may present as calcification of the basal ganglia, associated with seizures, Parkinson's disease, and cognitive difficulties.
Related conditions
{| cellpadding="5" | class="wikitable"
|-
! colspan="2" | Condition
! Appearance
! PTH levels
! Calcitriol
! Calcium
! Phosphates
! Imprinting
|-
| colspan="2" | Hypoparathyroidism
| Normal
| Low
| Low
| Low
| High
| Not applicable
|-
| rowspan="3" | Pseudohypoparathyroidism
| align="center" | Type 1A
| Skeletal defects
| High
| Low
| Low
| High
| Gene defect from mother (GNAS1)
|-
| align="center" | Type 1B
| Normal
| High
| Low
| Low
| High
| Gene defect from mother (GNAS1 and STX16)
|-
| align="center" | Type 2
| Normal
| High
| Low
| Low
| High
| ?
|-
| colspan="2" | Pseudopseudohypoparathyroidism
| Skeletal defects
| Normal
| Normal
| Normal
| Normal
| gene defect from father
|}
Causes
Hypoparathyroidism can have the following causes:
- Vitamin D deficiency or hereditary insensitivity to this vitamin (X-linked dominant).
- Malabsorption
- Kidney disease
- Medication: steroids, diuretics, some antiepileptics.
Other tests include ECG for abnormal heart rhythms, and measurement of blood magnesium levels.
Treatment
Severe hypocalcaemia, a potentially life-threatening condition, is treated as soon as possible with intravenous calcium (e.g., as calcium gluconate). Calcium gluconate can be given via a peripheral IV; however, other calcium formulations require infusion via a central venous catheter as the calcium can irritate peripheral veins and cause phlebitis. Calcium levels in the blood and urine (along with other electrolytes) must be monitored during long-term treatment of hypoparathyroidism and blood calcium levels are intentionally kept at the lower limits of normal, or mildly low, specifically to avoid hypercalciuria, kidney calcification and kidney damage. Recombinant human parathyroid hormone and teriparatide are also associated with a risk of hypercalcemia, hypercalciuria with associated kidney calcification and kidney damage.
Kidney ultrasound may be considered periodically to assess for any nephrocalcinosis for those on long-term therapy for hypoparathyroidism.