Physiologic Regulation of FGF-23

NCT00356512 | Completed

• 2 other identifiers: 06018806-D-0188
• Study Type: observational
• Target: 20
• Locations: 1 country
• Sites: 1

Brief Summary

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. ...

Conditions

Hypoparathyroidism

Keywords

Phosphate; Vitamin D; Hypoparathyroidism; Phosphatonin; Clamp

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Adult hypoparathyroid patients, as defined by low or inappropriately normal PTH levels despite hypocalcemia, who are on a stable treatment regimen of calcitriol and calcium supplementation, and who are willing to participate in the study will be eligible.
• Adult PHP1B patients as defined by the clinical syndrome of elevated PTH and phosphorus and confirmed by methylation analysis of the GNAS gene.

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

Sponsors & Collaborators

• National Institute of Dental and Craniofacial Research (NIDCR): lead

Study Sites (1)

National Institutes of Health Clinical Center, 9000 Rockville Pike

Bethesda, Maryland, 20892, United States

Location

Related Publications (3)

• Kumar R. Phosphatonin--a new phosphaturetic hormone? (lessons from tumour-induced osteomalacia and X-linked hypophosphataemia). Nephrol Dial Transplant. 1997 Jan;12(1):11-3. doi: 10.1093/ndt/12.1.11. No abstract available.

  PMID: 9027763 BACKGROUND

• Jonsson KB, Zahradnik R, Larsson T, White KE, Sugimoto T, Imanishi Y, Yamamoto T, Hampson G, Koshiyama H, Ljunggren O, Oba K, Yang IM, Miyauchi A, Econs MJ, Lavigne J, Juppner H. Fibroblast growth factor 23 in oncogenic osteomalacia and X-linked hypophosphatemia. N Engl J Med. 2003 Apr 24;348(17):1656-63. doi: 10.1056/NEJMoa020881.

  PMID: 12711740 BACKGROUND

• Yamazaki Y, Okazaki R, Shibata M, Hasegawa Y, Satoh K, Tajima T, Takeuchi Y, Fujita T, Nakahara K, Yamashita T, Fukumoto S. Increased circulatory level of biologically active full-length FGF-23 in patients with hypophosphatemic rickets/osteomalacia. J Clin Endocrinol Metab. 2002 Nov;87(11):4957-60. doi: 10.1210/jc.2002-021105.

  PMID: 12414858 BACKGROUND

MeSH Terms

Conditions

Hypoparathyroidism

Condition Hierarchy (Ancestors)

Parathyroid Diseases; Endocrine System Diseases

Study Design

• Study Type: observational
• Sponsor Type: NIH

Study Record Dates

• First Submitted: July 25, 2006
• First Posted: July 26, 2006
• Study Start: July 19, 2006
• Primary Completion: September 2, 2009
• Last Updated: July 2, 2017

Record last verified: 2009-09-02

Locations

US (1)