Causes of HPTH

Hypoparathyroidism mainly develops because of the following reasons:

1. Iatrogenic Hypoparathyroidism (result of surgery):
   
   The disease may develop if the glands are damaged during operation on the thyroid. They are removed unintentionally or the blood supplies to the glands are damaged. The risk of getting the complication is much less in the hands of a clever surgeon that has performed many of these operations. The risk of getting this complication is around 1%. The Endocrine surgeon should try as best he can to preserve all four parathyroid glands.
   
   Some patients get transient hypoparathyroidism after surgery. Some hospitals are careful and do auto transplantations during the operation. This means putting back peaces of the gland, usually to the muscle in the throat or arm. The hospitals also have the possibility to do a scintigraphy (picture) before operation, so they know where the parathyroid glands are situated. In addition some hospitals measure the PTH levels in the blood before and during surgery. Giving methylene blue into a vein before operation will colour the parathyroids blue during operation and make them more visible. Ultrasound is also a possibility.
   The disease may also develop after parathyroidea-surgery. This is more rare because the blood supply to the remaining parathyroid glands normally is intact when no thyroid tissue is removed. Some patients get Hypoparathyroidism (decreased production of the parathyroid hormone), while others are Anparathyroid ( no production of the hormone).
2. Primary Hypoparathyroidism:
   
   a) Ideopatic hypoparathyroidism:
   
   Some persons are born without enough parathyroid tissue. This may be linked to the family or occur isolated.
   Family idiopathic HPTH may be inherited as a sex-linked recessive, authosomal recessive or authosomal dominant disease.
   
   b) Pseudohypoparathyroidism:
   
   This is an inherited disease, which is characterised by to little response to the hormone. So the amount of the hormone is normal but the receptors are not functioning properly.
   
   
3. Hypoparathyroidism may also be present together with other diseases. Three of them are mentioned here:
   
   a) DiGeorge syndrome:
   
   DiGeorge syndrome is caused by the lack (deletion) from chromosome 22 (22Q11). This deletion means that several genes from this region are not present. It appears that the variation in the symptoms of the disease is related to the amount of genetic material lost in the chromosomal deletion. In Sweden they call the syndrome CATCH22. One of the symptoms of the disease are insufficient development of the parathyroid glands.
   
   b) Autoimmune polyendocrine syndrome, also called APECED or APS-1.
   
   APECED is a rare autoimmune disease affecting mainly the endocrine glands, but some other organs as well.
   
   The disease results because of mutations in just one gene, which makes the AIRE autoimmune regulator protein. Inheritence is autosomal recessive. That means that both parents have at least one faulty gene for the AIRE protein.
   
   Symptoms typically begin in childhood. The first signs in a young child can be one or several fits due to low blood calcium. If the cause is not recognised, death results.
   
   The most common features of APECED are parathyroid gland failure (affects calcium metabolism,), chronic susceptibility to Candida yeast infection and Addison's disease (adrenal failure). Other glands may also be involved in the disease.
   
   c) Albright's osteodystrophy.
   
   This is usually a sporadic genetic disease. The patients usually have pseudo hypoparathyroidism. The patients have a round face, short thick neck, obesity, shortening of metacarpals and metatarsals.