Trial Information

Pilot Study to Detect and Assess the Effect of Vitamin D Replacement on Gland Size by 4DCT in Patients With Primary Hyperparathyroidism (PHPT)

The Study Vitamin:

In patients with PHPT and a Vitamin D deficiency, Vitamin D supplements are routinely given
to bring Vitamin D blood levels up to a normal level before surgery on any abnormal
parathyroid glands. When patients have Vitamin D deficiency, they do not absorb calcium very
well, so the parathyroid glands have to work harder. This may cause the parathyroid glands
to become larger.

Screening Test:

Before you can take part in this study, you will have a "screening test" to help the doctor
decide if you are eligible to take part. Women who are able to have children must have a
negative blood (about 1 teaspoon) pregnancy test within two weeks before signing consent.

Baseline:

If you are found to be eligible to take part in this study, as part of your routine standard
of care, you will have a 4-dimensional computed tomography (4DCT) scan of the neck. This
4DCT will be used to find the size and location of your parathyroid glands to help the
surgeon in planning the surgery.

Vitamin D Administration:

You will receive Vitamin D pills to take at home, by mouth. You should take the Vitamin D at
the same time each day. If it causes an upset stomach, you should take it with food.

You will be given a study diary to record the days that you take the Vitamin D pills. You
will return the diary at the end of each cycle.

Cycle 1 During Cycle 1 (about the first 3 weeks of the study, +/- 1 week), you will take 3
Vitamin D pills per week about every other day (for example, Mondays, Wednesdays, and
Fridays).

At the end of Cycle 1, blood (about 1 teaspoon) will be drawn to check Vitamin D levels.

If your Vitamin D level is not high enough at this first Cycle 1 study visit, you will
repeat the Cycle 1 dosing schedule a second time. At the end of this second Cycle 1 dosing
schedule, you will have another blood test (about 1 teaspoon) to check your Vitamin D
levels. If your Vitamin D level is not high enough, you will be taken off study.

If your Vitamin D level is high enough after either your first or second Cycle 1 dosing
schedule, you will go to Cycle 2.

Cycle 2 During Cycle 2, the dosing schedule for Vitamin D is 2 pills per week for 6 weeks
(+/- 1 week). You should try to take the pill on the same day of the week.

At the end of Cycle 2, blood (about 1 teaspoon) will be drawn to check Vitamin D levels.

If your Vitamin D level is not high enough at this first Cycle 2 study visit, you will
repeat the Cycle 2 dosing schedule a second time. At the end of this second Cycle 2 dosing
schedule, you will have another blood test (about 1 teaspoon) to check your Vitamin D
levels. If your Vitamin D level is not high enough, you will be taken off study.

If your Vitamin D level is high enough after either your first or second Cycle 2 dosing
schedule, you will go to Cycle 3.

Cycle 3 During Cycle 3, the dosing schedule for Vitamin D is 2 pills per week for 6 weeks
(+/- 1 week).

At the end of Cycle 3, blood (about 1 teaspoon) will be drawn to check Vitamin D levels.

If your Vitamin D level is high enough, you will have another 4DCT scan of your neck, for
the purpose of this research study. This second scan will be used to see if your parathyroid
glands have changed in size. Before this second scan, blood (about 1/2 teaspoon) will be
drawn to check your kidney function.

If your Vitamin D level is not high enough, you will be taken off study.

Routine Surgical Treatment:

Within 3 weeks after your second 4DCT scan, your routine surgery for PHPT will be performed.
You will sign a separate consent form and its risks will be described in more detail at
that time. Your removed parathyroid glands will examined.

Length of Study:

Your active participation in this study will be over after you have surgery. If the side
effects of PHPT indicate that you may need to have parathyroid surgery earlier, you will be
taken off study early and have the surgery as soon as possible.

This is an investigational study. Vitamin D supplements are commercially available and FDA
approved for use in patients with PHPT and a Vitamin D deficiency to bring the Vitamin D
blood levels to normal before surgery. It is considered experimental to have a second 4DCT
scan after your Vitamin D levels are high enough. While you are on study, study-related
procedures (such as the second 4DCT scan and the blood test before the scan) will be
performed at no cost to you.

Up to 22 patients will take part in this study. All will be enrolled at M. D. Anderson.