Discordant Localization in Primary Hyperparathyroidism

Yes. She has biochemical primary hyperparathyroidism with an elevated calcium and an elevated PTH, plus two classic complications: recurrent nephrolithiasis and osteoporosis with a femoral neck T-score of −2.8. Guideline criteria for surgery include serum calcium more than 1 mg/dL above the upper limit of normal, age under 50 years, reduced bone density, nephrolithiasis, and urinary calcium above 400 mg/day. She meets at least the calcium, bone, and stone criteria even though her urinary calcium is 320 mg/day.

Preoperative issues:

• Confirm the diagnosis with repeat calcium and PTH and exclude secondary causes, especially vitamin D deficiency and renal insufficiency.
• Review hydrochlorothiazide, which can raise serum calcium by increasing renal reabsorption. It should not be stopped abruptly without blood pressure planning, but the result should be interpreted with that effect in mind.
• Exclude familial hypocalciuric hypercalcemia using the calcium-to-creatinine clearance ratio when there is doubt; her high urinary calcium makes that diagnosis unlikely.
• Correct vitamin D deficiency if present, ensure hydration, and assess bone health.
• Screen for multigland disease and consider MEN1 only if there are suggestive features; she has no family history.

The operation is justified to prevent stone recurrence and further bone loss, not merely to normalize a number.

A negative sestamibi scan does not rule out a single adenoma. Ultrasound and sestamibi are complementary, and concordance is helpful but not required for a first-time operation by an experienced parathyroid surgeon.

Preferred plan: A focused left parathyroidectomy based on the ultrasound, with intraoperative PTH monitoring. The surgeon should be prepared to convert to a bilateral neck exploration if the abnormal gland is not found or if the PTH fails to fall. Frozen section can confirm parathyroid tissue but does not replace surgical judgment about whether the gland is enlarged and whether four glands have been identified.

When to choose bilateral exploration up front:

• The surgeon is less experienced or intraoperative PTH is unavailable.
• There is suspicion of multigland disease, familial disease, or lithium-associated hyperparathyroidism.
• The ultrasound finding is equivocal or inconsistent with the expected embryologic location.

Additional imaging such as four-dimensional CT or selective venous sampling is generally reserved for reoperative cases or when noninvasive studies are discordant and the surgeon needs better localization. In this first operation, exploration with PTH guidance is appropriate.

A fall from 142 to 68 pg/mL is a 52% decrease, which meets the Miami criterion of at least a 50% fall at 10 minutes and predicts cure in most patients. It is close to the threshold, so I would confirm the result with a 20-minute measurement if there is any concern about assay variability or if the 10-minute sample was drawn before adequate gland removal.

If the 20-minute value remains at least 50% below baseline: Conclude that the hypersecreting gland has been removed, close the incision, and plan postoperative calcium monitoring. Do not perform an unnecessary bilateral exploration solely because the sestamibi was negative.

If the fall is less than 50%: Look for another enlarged gland. Check the ipsilateral side first, then explore the contralateral side and the usual ectopic locations, including the thymus, thyrothymic ligament, and tracheoesophageal groove. A rise or failure to fall suggests multigland disease or a missed adenoma.

Postoperatively, monitor for hypocalcemia, supplement calcium and vitamin D as needed, and counsel her that bone density and stone risk should improve after successful surgery.