SUN-832 - Primary Hyperparathyroidism Presenting as Nephrolithiasis in a Young Woman

Background:
Primary hyperparathyroidism (PHPT) is uncommon in young adults and more often diagnosed later in life. In younger patients, evaluation is important because hereditary etiologies and long-term renal or skeletal complications may be more likely. Nephrolithiasis may be the presenting manifestation even in otherwise asymptomatic patients.

Case Presentation:
A 23-year-old woman with developmental hip dysplasia and mood disorder was referred for evaluation of hypercalcemia and hyperparathyroidism after recurrent nephrolithiasis over the preceding year. Kidney stones were first identified on abdominal imaging obtained for unrelated gynecologic evaluation, and she spontaneously passed one stone. She denied symptoms of hypercalcemia including polyuria, polydipsia, constipation, abdominal pain, fatigue, fractures, or bone pain.

Laboratory studies showed persistent mild hypercalcemia with serum calcium 10.4–11.2 mg/dL (reference 8.6–10.3), elevated ionized calcium up to 1.45 mmol/L, and inappropriately elevated intact PTH of 123.3–138.6 pg/mL. Renal function was normal and prior vitamin D deficiency had been corrected. She reported lithium exposure for less than one week after hypercalcemia had already been documented, making lithium-induced hyperparathyroidism unlikely. There was no known family history of nephrolithiasis, hypercalcemia, or MEN-associated tumors.

Neck ultrasound and sestamibi SPECT/CT localized a 7 mm lesion inferior to the left thyroid lobe, consistent with parathyroid adenoma. Given age < 50 years and nephrolithiasis, she met criteria for surgery. She underwent focused left inferior parathyroidectomy. Intraoperative PTH declined from 123.9 pg/mL pre-excision to 66.1 pg/mL and then 49.1 pg/mL post-excision. Pathology demonstrated an enlarged hypercellular parathyroid adenoma. She remained clinically well postoperatively without hypocalcemia.

Discussion:
This case highlights several important features of PHPT in young adults. First, even mild biochemical abnormalities may be clinically significant when accompanied by nephrolithiasis. Second, PHPT should remain the leading consideration when calcium elevation coexists with nonsuppressed PTH, despite potential confounders such as transient lithium exposure or prior vitamin D deficiency. Third, younger age at diagnosis raises consideration for hereditary syndromes such as MEN1, MEN2A, CDC73-related disorders, or familial isolated hyperparathyroidism, and genetic counseling/testing may be appropriate.

Conclusion:
PHPT should be considered in young patients presenting with kidney stones, even when hypercalcemia is mild and symptoms absent. Early diagnosis and curative parathyroidectomy can prevent recurrent stones and long-term skeletal or renal complications.

*Unless otherwise noted, all abstracts presented at ENDO must not be released to the press or the public until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.*