Parathyroid hormone (PTH), also called parathormone or parathyrin, is a peptide hormone secreted by the parathyroid glands that regulates the serum calcium concentration through its effects on bone, kidney, and intestine.
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, 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 a number of 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. However teriparatide, brand name Forteo, a biosimilar peptide to parathyroid hormone, may be given by injection.
Hyperparathyroidism is an increase in parathyroid hormone (PTH) levels in the blood. This occurs from a disorder either within the parathyroid glands or outside the parathyroid glands. Symptoms of hyperparathyroidism are caused by inappropriately normal or elevated blood calcium leaving the bones and flowing into the blood stream in response to increased production of parathyroid hormone. In healthy people, when blood calcium levels are high, parathyroid hormone levels should be low. With long-standing hyperparathyroidism, the most common symptom is kidney stones. Other symptoms may include bone pain, weakness, depression, confusion, and increased urination. Both primary and secondary may result in osteoporosis.
Hyperphosphatemia is an electrolyte disorder in which there is an elevated level of phosphate in the blood. Most people have no symptoms while others develop calcium deposits in the soft tissue. Often there is also low calcium levels which can result in muscle spasms.
Parathyroidectomy is the surgical removal of one or more of the (usually) four parathyroid glands. This procedure is used to remove an adenoma or hyperplasia of these glands when they are producing excessive parathyroid hormone (PTH): hyperparathyroidism. The glands are usually four in number and located adjacent to the posterior surface of the thyroid gland, but their exact location is variable. When an elevated PTH level is found, a sestamibi scan or an ultrasound may be performed in order to confirm the presence and location of abnormal parathyroid tissue.
Cinacalcet, sold under the brand name Sensipar among others, is a medication used to treat secondary hyperparathyroidism, parathyroid carcinoma, and primary hyperparathyroidism.
Renal osteodystrophy/adynamic bone disease is currently defined as an alteration of bone morphology in patients with chronic kidney disease (CKD). It is one measure of the skeletal component of the systemic disorder of chronic kidney disease-mineral and bone disorder (CKD-MBD). The term "renal osteodystrophy" was coined in 1943, 60 years after an association was identified between bone disease and kidney failure.
Primary hyperparathyroidism is usually caused by a tumor within the parathyroid gland. The symptoms of the condition relate to the elevated calcium levels, which can cause digestive symptoms, kidney stones, psychiatric abnormalities, and bone disease.
Osteitis fibrosa cystica, is a skeletal disorder resulting in a loss of bone mass, a weakening of the bones as their calcified supporting structures are replaced with fibrous tissue, and the formation of cyst-like brown tumors in and around the bone. Osteitis fibrosis cystica, abbreviated OFC, also known as osteitis fibrosa, osteodystrophia fibrosa, and von Recklinghausen's disease of bone, is caused by hyperparathyroidism, which is a surplus of parathyroid hormone from over-active parathyroid glands. This surplus stimulates the activity of osteoclasts, cells that break down bone, in a process known as osteoclastic bone resorption. The hyperparathyroidism can be triggered by a parathyroid adenoma, hereditary factors, parathyroid carcinoma, or renal osteodystrophy. Osteoclastic bone resorption releases minerals, including calcium, from the bone into the bloodstream, causing both elevated blood calcium levels, and the structural changes which weaken the bone. The symptoms of the disease are the consequences of both the general softening of the bones and the excess calcium in the blood, and include bone fractures, kidney stones, nausea, moth-eaten appearance in the bones, appetite loss, and weight loss.
Secondary hyperparathyroidism is the medical condition of excessive secretion of parathyroid hormone (PTH) by the parathyroid glands in response to hypocalcemia, 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.
Tertiary Hyperparathyroidism is a condition involving the overproduction of the hormone, parathyroid hormone, produced by the parathyroid glands. The parathyroid glands are involved in monitoring and regulating blood calcium levels and respond by either producing or ceasing to produce parathyroid hormone. Anatomically, these glands are located in the neck, Para-lateral to the thyroid gland, which does not have any influence in the production of parathyroid hormone. Parathyroid hormone is released by the parathyroid glands in response to low blood calcium circulation. Persistent low levels of circulating calcium are thought to be the catalyst in the progressive development of adenoma in the parathyroid glands resulting in primary hyperparathyroidism. While primary hyperparathyroidism is the most common form of this condition, secondary and tertiary are thought to result due to chronic kidney disease (CKD). Estimates of CKD prevalence in the global community range from 11-13% which translate to a large portion of the global population at risk of developing tertiary hyperparathyroidism. Tertiary hyperparathyroidism was first described in the late 1960s and had been misdiagnosed as primary prior to this. Unlike primary hyperparathyroidism, the tertiary form presents as a progressive stage of resolved secondary hyperparathyroidism with biochemical hallmarks that include elevated calcium ion levels in the blood, hypercalcemia, along with autonomous production of parathyroid hormone and adenoma in all four parathyroid glands. Upon diagnosis treatment of tertiary hyperparathyroidism usually leads to a surgical intervention.
The calcium-sensing receptor (CaSR) is a Class C G-protein coupled receptor which senses extracellular levels of calcium ions. It is primarily expressed in the parathyroid gland, the renal tubules of the kidney and the brain. In the parathyroid gland, it controls calcium homeostasis by regulating the release of parathyroid hormone (PTH). In the kidney it has an inhibitory effect on the reabsorption of calcium, potassium, sodium, and water depending on which segment of the tubule is being activated.
Parathyroid carcinoma is a rare cancer resulting in parathyroid adenoma to carcinoma progression. It forms in tissues of one or more of the parathyroid glands.
Many conditions are associated with disorders of the function of the parathyroid gland. Some disorders may be purely anatomical resulting in an enlarged gland which will raise concern. Such benign disorders, such as parathyroid cyst, are not discussed here. Parathyroid diseases can be divided into those causing hyperparathyroidism, and those causing hypoparathyroidism.
A calcimimetic is a pharmaceutical drug that mimics the action of calcium on tissues, by allosteric activation of the calcium-sensing receptor that is expressed in various human organ tissues. Calcimimetics are used to treat secondary hyperparathyroidism (SHPT).
Abaloparatide is a parathyroid hormone-related protein (PTHrP) analog drug used to treat osteoporosis. Like the related drug teriparatide, it is an anabolic agent.
Recombinant human parathyroid hormone, sold under the brand names Preotact and Natpara, is an artificially manufactured form of the parathyroid hormone used to treat hypoparathyroidism. Recombinant human parathyroid hormone is used in the treatment of osteoporosis in postmenopausal women at high risk of osteoporotic fractures. A significant reduction in the incidence of vertebral fractures has been demonstrated.
Chronic kidney disease–mineral and bone disorder (CKD-MBD) is one of the many complications associated with chronic kidney disease. It represents a systemic disorder of mineral and bone metabolism due to CKD manifested by either one or a combination of the following:
Evocalcet is a drug for the treatment of hyperparathyroidism. It acts as a calcium-sensing receptor agonist.
Upacicalcet is a drug used to treat secondary hyperparathyroidism (SHPT) - a disease of the parathyroid gland - in dialysis patients. It was approved as Upasita in Japan in June 2021. The drug is given intravenously. The active ingredient is used in the form of its sodium salt.
