Physiologic Regulation of FGF-23

Completed

Conditions studied: Hypoparathyroidism

In brief

This study will explore the regulation of fibroblast growth factor-23 (FGF-23). It is a hormone recently identified as a regulator of the blood levels of phosphorus and vitamin D, both of which are essential for overall health and especially important for bone health. The parathyroid hormone (PTH) regulates phosphorus and calcium, but people with hypoparathyroidism or pseudohypoparathyroidism do not have sufficient PTH action. There are genetic diseases that influence FGF-23, causing abnormal metabolism of phosphorus and vitamin D, thus affecting the bones. Also, there are rare tumors that may cause overproduction of FGF-23 causing debilitating bone disease. Patients ages 18 and older who have low PTH levels, or are resistant to PTH action, and take calcitriol and calcium supplements, who are not pregnant, and who do not have kidney disorders may be eligible for this study. During the 4-day study, patients will be provided with a controlled diet that has a lower than usual phosphorus content. On day 1, patients will be admitted to the NIH Clinic Center and undergo blood and urine tests to measure calcium, phosphorus, vitamin D, and FGF-23. They will continue with their regular medicine for hypoparathyroidism. On that day and throughout the study, patients will fast from 10:00 p.m. to 8:00 a.m. the following day. On day 2, patients will continue fasting until 4:00 p.m. A tube will be placed in the vein of each arm: one for drawing blood and the other for infusing calcium. Just one intravenous (IV) line will be used on the other days. Patients will receive calcium chloride for 8 hours, at a dose carefully monitored by a machine. The purpose is to bring the blood calcium level to the high normal range or just above. Blood and urine samples will be collected periodically, to check for effects of calcium chloride on FGF-23 and PTH. On days 3 and 4, patients will not take calcitriol and calcium but will receive injections of PTH, under the skin, two times each day. On day 3, blood and urine samples will be again be collected for analysis. On day 4, patients will receive one dose of calcitriol by IV. The total amount of blood drawn during this study will be about 5 ounces. ...

Key facts

Study ID

NCT00356512

Run by

National Institute of Dental and Craniofacial Research (NIDCR)

People needed

20

Starts

2006-07-19

Last updated by the study team

2017-07-02

Who can join

Age: 18 and older. Sex: any. Healthy volunteers: not accepted.

You may not qualify if…

• Renal insufficiency as evidenced by a creatinine clearance of less than 50 ml/min
• Medically unstable patients
• Uncontrolled comorbid conditions, e.g., diabetes, coronary artery disease, congestive heart failure, or cerebrovascular disease.
• Digitalis therapy
• Patients on diuretic therapy, especially thiazides
• Pregnant and lactating women
• Patients whose hypoparathyroidism is caused by severe calcium-sensing receptor defects. These patients begin to have marked symptoms of "hypercalcemia" when the serum calcium is in the mid-normal range.
• Patients under 18 years of age
• Patients with history of any bone cancer, skeletal metastases or previous radiotherapy to the skeleton, unexplained elevations of serum alkaline phosphatase

Where it is running

• National Institutes of Health Clinical Center, 9000 Rockville Pike — Bethesda, Maryland, United States

Full record on ClinicalTrials.gov

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