Hypoparathyroidism (HP) (synonyms: Hypoparathyroidism; parathyroid insufficiency; parathyroid hormone deficiency; ICD-10-GM E20.-: Hypoparathyroidism) describes an underactivity of the parathyroid glands as a result of which the messenger substance parathyroid hormone (PTH) is not or insufficiently produced. In most people, the parathyroid glands (lat.: Glandulae parathyroideae) consist of four organs about the size of a lentil and are located in the neck behind the thyroid gland (lat. Glandula thyreoidea or Glandula thyroidea), below the larynx. They are also called epithelial corpuscles.
Parathyroid hormone (PTH) is particularly important in the context of calcium metabolism. If the serum calcium level is too low, the parathyroid hormone causes osteoclasts (cells that break down bone) to be activated, thereby mobilizing calcium and phosphate from the bone. Bones are the main storehouse for the mineral calcium. In the presence of vitamin D, parathyroid hormone increases calcium absorption (calcium uptake) in the small intestine and calcium reabsorption (calcium reuptake) in the kidney. Another effect of parathyroid hormone is stimulation of phosphate excretion by the kidneys. The physiological antagonist of parathyroid hormone is calcitonin, which is produced in the C-cells of the thyroid gland.In the case of PTH deficiency, the mechanisms described above do not take place or take place only to a limited extent. Consequently, hypocalcemia (calcium deficiency), hyperphosphatemia (phosphate excess), and decreased 1,25-dihydroxyvitamin D levels occur.
The following forms of hypoparathyroidism (parathyroid hypofunction) can be distinguished:
- Idiopathic hypoparathyroidism (ICD-10-GM E20.0).
- Pseudohypoparathyroidism (ICD-10-GM E20.1)
- Other hypoparathyroidism (ICD-10-GM E20.8)
- Hypoparathyroidism, unspecified (ICD-10-GM E20.9)
According to the cause, the following forms of hypoparathyroidism can be distinguished:
- Primary hypoparathyroidism (congenital hypoparathyroidism) – congenital (very rare) – see below “Causes”.
- Secondary hypoparathyroidism – due to damage to the parathyroid glands, especially after thyroid surgery (postoperative hypoparathyroidism) (most common).
- Idiopathic hypoparathyroidism – with no apparent cause (rare).
Postoperative hypoparathyroidism occurs in 500-1,000 people annually.
The prevalence (disease frequency) for postoperative hypoparathyroidism is 0.5-6.6% after total thyroidectomy (thyroidectomy) (in Germany).
Course and prognosis: The effects of hypoparathyroidism can be remedied or prevented by appropriate therapy, which focuses on normalization of electrolytes – calcium, phosphate – as well as vitamin D. The prognosis is favorable as long as the treatment is carried out consistently. If the therapy is not optimal, secondary diseases or complications must be expected.As part of the treatment, the calcium level should be closely monitored to avoid hypercalcemic syndrome. In the worst case, a hypercalcemic crisis can develop (see “Consequential diseases”). However, this happens extremely rarely. Patients with hypoparathyroidism are given an emergency card.
