Secondary hyperparathyroidism  is the medical condition of excessive secretion of parathyroid hormone (PTH) by the parathyroid glands in response to hypocalcemia (low blood calcium levels), with resultant hyperplasia of these glands. This disorder is primarily seen in patients with chronic kidney failure. It is sometimes abbreviated "SHPT" in medical literature. Signs and symptoms
Bone and joint pain are common, as are limb deformities. The elevated PTH has also pleiotropic effects on the blood, immune system, and neurological system. Cause
Chronic kidney failure is the most common cause of secondary hyperparathyroidism. Failing kidneys do not convert enough vitamin D to its active form, and they do not adequately excrete phosphate. When this happens, insoluble calcium phosphate forms in the body and removes calcium from the circulation. Both processes lead to hypocalcemia and hence secondary hyperparathyroidism. Secondary hyperparathyroidism can also result from malabsorption (chronic pancreatitis, small bowel disease, malabsorption-dependent bariatric surgery) in that the fat-soluble vitamin D can not get reabsorbed. This leads to hypocalcemia and a subsequent increase in parathyroid hormone secretion in an attempt to increase the serum calcium levels. A few other causes can stem from inadequate dietary intake of calcium, a vitamin D deficiency, or steatorrhea. Diagnosis
The PTH is elevated due to decreased levels of calcium or 1,25-dihydroxy-vitamin D3. It is usually seen in cases of chronic kidney disease or defective calcium receptors on the surface of parathyroid glands. Treatment
If the underlying cause of the hypocalcemia can be addressed, the hyperparathyroidism will resolve.
Trichilemmal carcinoma  is a cutaneous condition reported to arise on sun-exposed areas, most commonly the face and ears. : 674

See also
Trichilemmoma
Skin lesionA similar tumor, although in the nail bed, is called onycholemmal. References


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