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.PTH influences bone remodeling, which is an ongoing process in which bone tissue is alternately resorbed and rebuilt over time. PTH is secreted in response to low blood serum calcium (Ca2+) levels. PTH indirectly stimulates osteoclast activity within the bone matrix (osteon), in an effort to release more ionic calcium (Ca2+) into the blood to elevate a low serum calcium level. The bones act as a (metaphorical) "bank of calcium" from which the body can make "withdrawals" as needed to keep the amount of calcium in the blood at appropriate levels despite the ever-present challenges of metabolism, stress, and nutritional variations. PTH is "a key that unlocks the bank vault" to remove the calcium. PTH is secreted primarily by the chief cells of the parathyroid glands. The gene for PTH is located on chromosome 11. It is a polypeptide containing 84 amino acids, which is a prohormone. It has a molecular mass around 9500 Da. Its action is opposed by the hormone calcitonin. There are two types of PTH receptors. Parathyroid hormone 1 receptors, activated by the 34 N-terminal amino acids of PTH, are present at high levels on the cells of bone and kidney. Parathyroid hormone 2 receptors are present at high levels on the cells of central nervous system, pancreas, testes, and placenta.
Order Mucorales (mucormycosis)
Family Mucoraceae
Absidia (Absidia corymbifera)
Apophysomyces (Apophysomyces elegans and Apophysomyces trapeziformis)
Mucor (Mucor indicus)
Rhizomucor (Rhizomucor pusillus)
Rhizopus (Rhizopus oryzae)
Family Cunninghamellaceae
Cunninghamella (Cunninghamella bertholletiae)
Family Thamnidiaceae
Cokeromyces (Cokeromyces recurvatus)
Family Saksenaeaceae
Saksenaea (Saksenaea vasiformis)
Family Syncephalastraceae
Syncephalastrum (Syncephalastrum racemosum)
Order Entomophthorales (entomophthoramycosis)
Family Basidiobolaceae
Basidiobolus (Basidiobolus ranarum)
Family Ancylistaceae
Conidiobolus (Conidiobolus coronatus/Conidiobolus incongruus)

Epidemiology
Zygomycosis has been found in survivors of the 2004 Indian Ocean earthquake and tsunami and in survivors of the 2011 Joplin, Missouri tornado. Symptoms
In the primary cutaneous form, the lesions are usually painful and necrotic, with black eschar, accompanied by a fever. Patients will usually present with a history of poorly controlled diabetes or malignancy. Myocutaneous infections may lead to amputation. Pulmonary tract infections seen with lung transplant patients, who are at high risk for fatal invasive mycoses. Rhinocerebral infection is characterized by paranasal swelling with necrotic tissues. Patient may have hemorrhagic exudates (tissue fluid from lesions tinged with blood) from the nose and eyes as the fungi penetrate through blood vessels and other anatomical structures. Diagnosis
Diagnosis is done with potassium hydroxide (KOH) preparation in tissue. On light microscopy, there will be broad, ribbon-like septate hyphae with 90 degree angles on branches. KOH wet mount of the black eschar will show aseptate fungal hyphae with right angle branching. Periodic Acid Schiff (PAS) staining will reveal similar broad hyphae in the dermis and cutis. Fungal culture can also confirm the organism. Diagnosis remains difficult due to the lack of laboratory tests as mortality remains high.