Vitamin D Repletion in Primary Hyperparathyroidism

Primary hyperparathyroidism (PHPT) is a common disease in which the parathyroid glands
produce excessive amounts of parathyroid hormone (PTH), which regulates calcium levels. In
primary hyperparathyroidism, high levels of PTH remove too much calcium from bones and
deposit the excess calcium in the blood, which is then filtered into the urine by the
kidneys. Bone health is threatened by the excess calcium loss which weakens the structure of
the bones.

Many patients with primary hyperparathyroidism also have low vitamin D (25OHD) levels which
is thought to further impair bone health. Recent medical guidelines recommend treating
patients with primary hyperparathyroidism who have low vitamin D levels with oral vitamin D
but the optimal vitamin D dose and rate of repletion is unclear. It is, therefore, important
to determine if replenishing Vitamin D will improve bone health in primary
hyperparathyroidism, and if so, to assess the impact of the rate of vitamin D repletion.

Inclusion Criteria:

- Diagnosed PHPT, defined by an elevated serum calcium level (we will not study
normocalcemic PHPT) with elevated or inappropriately normal PTH levels.

- Vitamin D3 less than 30 ng/ml

Exclusion Criteria:

- Patients with familial hyperparathyroid syndromes

- Current or past use of the following medications: bisphosphonate within past 2 years,
use of lithium or thiazide diuretics, current use of cinacalcet, use of aluminum
containing medications, cimetidine, colestipol, or orlistat

- Malignancy, except cured basal or squamous cell skin carcinoma or other cured cancers
that are at least five years free from recurrence

- History or current diagnosis of certain medical diseases (including sarcoidosis,
active infectious granulomatous disease, HIV/AIDS, chronic kidney disease (serum
creatinine > 1.5 mg/dL), liver disease; GI diseases known to affect calcium
metabolism; secondary hyperparathyroidism);

- We will also exclude patients with calcium above 11.5 mg/dL, urine calcium above 350
mg/day, and active nephrolithiasis because vitamin D repletion could potentially
exacerbate hypercalcemia or hypercalciuria

- Other exclusions include protected individuals (institutionalized), prisoners, and any
other prospective participant who might not be able to give voluntary informed
consent.