This study will determine whether a synthetic form of human parathyroid hormone (PTH) can control hypoparathyroidism and will examine the drug's effects on bone. Blood calcium and phosphate levels in patients with hypoparathyroidism are difficult to control with the current standard treatment of calcitriol and calcium supplementation. Calcium levels in the urine may be elevated at the same time that blood calcium levels are normal. This spilling of excessive calcium into the urine can lead to kidney damage.

Patients between 9 and 55 years of age with hypoparathyroidism may be eligible for this study. Participants

take standard calcitriol therapy for the first year of the study and start PTH after 1 year. After 1 year on PTH, they are given the option to continue the drug for an additional 3 years.

Patients are admitted to the NIH Clinical Center for 4-6 days at the start of the study, at the end of the first year, and at the end of the second year (and at year 5 for those who continue on PTH for an additional 3 years) for the following procedures:

" Daily 24-hour urine collection.

" Daily blood draw for calcium and phosphorous levels and for calcium-regulating hormones.

" Blood draw every 2 hours for 24 hours to measure blood calcium, phosphorus, and magnesium levels (admission 3 only). For this test blood samples are collected through a catheter (plastic tube) placed in a vein in the arm or hand to avoid multiple needle sticks.

" Questionnaire and 6-minute walk test to determine fatigue

" Bone biopsy to test treatment response. Before the biopsy, patients are given a regimen of the antibiotic tetracycline or demeclocycline. The drug is absorbed by the bone, "labeling" it in a way that permits investigators to learn more about the bone's biology. For the biopsy, the patient is given a sedative to cause drowsiness. The skin over the hipbone is numbed with an injection of anesthetic into the skin, through the underlying tissues, and onto the surface of the bone. A larger needle is then inserted into the bone itself, and a sample of bone tissue is withdrawn through the needle. More sedative or anesthetic may be given to lessen any pain.

Every week for the first month of the study and then twice a month, patients go to a laboratory for a 24-hour urine collection. Every 6 months, they come to the NIH outpatient clinic for a physical exam, blood and urine tests, and a dual energy X-ray absorptiometry (DXA) scan to measure bone density.