Suspected Deficient Activation of Vitamin D in Patients With Secondary Hyperparathyroidism

University of Maryland, Baltimore20 enrolled

Overview

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.

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.

Study Type

INTERVENTIONAL

Allocation

NON_RANDOMIZED

Purpose

DIAGNOSTIC

Masking

NONE

Enrollment

Conditions

Secondary Hyperparathyroidism

Interventions

TeriparatideDRUG

Teriparatide will be given by continuous intravenous infusion at a rate of 12 pmol/kg/hr for 8 hours to both "patients" and "controls"

Eligibility

Sex: FEMALEMin age: 40 YearsMax age: 59 YearsHealthy volunteers:

Medical Language ↔ Plain English

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

Locations (1)

University of Maryland School of Medicine Division of Endocrinology

Baltimore, Maryland, United States

Outcomes

Primary Outcomes

The Level of Activated Vitamin D (1,25-dihydroxyvitamin D) After Parathyroid Hormone Infusion at Baseline, 4 and 8 Hours

1,25-D was measured at baseline, 4 and 8 hours after PTH infusion

Time frame: baseline, 4 and 8 hours after start of infusion

Secondary Outcomes

The Number of Patients With Mutations in CYP27B1

CYP27B1 gene (the gene for 25-hydroxyvitamin D-1-alpha hydroxylase) was sequenced for all in patient group and compared with published control data

Time frame: blood samples taken at baseline and sequenced over several days

Data from ClinicalTrials.gov

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