Suspected Deficient Activation of Vitamin D in Patients With Secondary Hyperparathyroidism

Not Applicable

Completed

Brief Summary: The purpose of this study is to determine if a reduction in the enzyme 1-hydroxylase, which activates Vitamin D, is the cause of overactivity of the parathyroid glands (called secondary hyperparathyroidism - normal blood calcium and elevated parathyroid hormone) in a selected group of young patients with normal kidney function.

Detailed Description: Vitamin D, an essential nutrient, is produced by the skin after sunlight shines on it. Vitamin D must then be activated by both the liver and the kidneys to perform its function of maintaining strong bones and helping to prevent heart disease, infection, diabetes and cancer. Reduced kidney activation of Vitamin D occurs with advanced age and with all kidney diseases. We have identified a small group of patients who appear to have reduced ability of the kidneys to activate vitamin D, even though they are young and do not have chronic kidney disease. In these patients, we are comparing the ability of their kidneys to activate Vitamin D to that of healthy controls. To stimulate the kidneys to activate Vitamin D, we are giving parathyroid hormone intravenously over 8 hours and collecting blood and urine at baseline, 4 and 8 hours. This type of parathyroid infusion does not cause side effects. The gene that controls this activation is also being studied (by a simple blood test) to look for abnormalities. We are now actively recruiting healthy controls for this study.

Recruitment & Eligibility

Inclusion Criteria

Caucasian female
Age 40-59 years
Serum creatinine < 1.3 and estimated glomerular filtration rate (GRF) > 60
Serum calcium in the normal range (for U Md lab 8.6-10 mg/dl)
Parathyroid hormone in the normal range (for U Md lab 12-54 pg/ml)
Normal 25-hydroxyvitamin D level (30 ng/ml or higher)
For women of childbearing age, non-pregnant (based on negative urine pregnancy test on the morning of the teriparatide infusion)

Exclusion Criteria

Non-caucasian
Age under 40 and over 59 years
Male
Serum creatinine over 1.3 or estimated glomerular filtration rate (GFR) < 60
Abnormal serum calcium (for U Md lab, below 8.6 or above 10 mg/dl)
Abnormal parathyroid hormone (for U Md lab, above 65 or below 12 pg/ml)
For women of childbearing age, non-pregnant (based on urine pregnancy test on the morning of the teriparatide infusion)
History of bone radiation
History of Paget disease of bone
History of bone malignancy or metastases
History of allergy or sensitivity to Forteo

Arm && Interventions

Group	Intervention	Description
teriparatide control	Teriparatide	control subject
Teriparatide Patient	Teriparatide	Patient with secondary hyperparathyroidism

Primary Outcome Measures

Name	Time	Method
The Level of Activated Vitamin D (1,25-dihydroxyvitamin D) After Parathyroid Hormone Infusion at Baseline, 4 and 8 Hours	baseline, 4 and 8 hours after start of infusion	1,25-D was measured at baseline, 4 and 8 hours after PTH infusion

Secondary Outcome Measures

Name	Time	Method
The Number of Patients With Mutations in CYP27B1	blood samples taken at baseline and sequenced over several days	CYP27B1 gene (the gene for 25-hydroxyvitamin D-1-alpha hydroxylase) was sequenced for all in patient group and compared with published control data