Calcitonin Pre-treatment to Improve SPECT-CT Sensitivity

Inclusion Criteria: * Diagnosis of primary hyperparathyroidism * Non-localizing SPECT-CT performed within 365 days prior to consent to participate in study * Patient desires surgical intervention for treatment of PHPT * No contraindications to 99mTC-Sestamibi * No contraindications to treatment with calcitonin * Serum calcium level prior to non-localizing SPECT-CT is ≥10.5 mg/dL * Patient consents to participate and undergo second SPECT-CT for purposes of research Exclusion Criteria: * Previous surgery to the neck, including resection of parathyroid tissue, except where end organ damage is present and further surgical intervention is medically necessary * Contraindication to 99mTC-Sestamibi SPECT-CT as evidenced by allergic reaction or adverse event during index SPECT-CT * Allergy to calcitonin * Hypocalcemia (contraindication to calcitonin) * Vitamin D deficiency (contraindication to calcitonin) * Previous treatment with radioactive iodine * New prescription of thyroid medication (levothyroxine, armour thyroid tablets, etc. must be taken at time of index scan and research scan) * Lithium exposure within one year of SPECT-CT (index and research scans) * Secondary hyperparathyroidism * Benign familial hypocalciuric hypercalcemia * Known malignancy, particularly multiple endocrine neoplasia * New prescription of thiazide diuretic, (thiazide diuretic must have been taken at the time of index scan and second scan) * Currently taking calcium channel blockers * Pregnancy