Diagnosis, natural history, and treatment of primary hyperparathyroidism

Normal parathyroid hormone levels in a diabetic patient with parathyroid adenoma

OBJECTIVE

The incidence of diabetes mellitus in patients with primary hyperparathyroidism and, conversely, primary hyperparathyroidism in diabetic patients are approximately threefold higher than the respective expected prevalence in the general populace. The diagnosis is straightforward when the patient presents hypercalcemia and inappropriately elevated serum parathyroid hormone (PTH) levels. We report a case of parathyroid adenoma in a diabetic patient with persistent hypercalcemia and normal PTH levels.

PATIENT

A 50-year-old female patient who was referred to our outpatient clinic presented with persistent hypercalcemia (serum Ca levels between 10.5 and 11 mg/dl) with a normal serum intact PTH level of 46.1 pg/ml. Her blood pressure was 120/80 mmHg, and she was being treated with antihypertensive therapy. Her HbA1c was 7.2%, and her triglycerides were in the normal range. A bone densitometry exam revealed osteopenia of radius -1.39, femoral neck -1.39, and the total hip -1.04. A neck ultrasound revealed a mass of 13 mm next to the inferior and posterior of the right thyroid lobe. A dual phase Tc-99m-sestamibi scan revealed an area of increased uptake in the same region, which is indicative of a parathyroid adenoma. The parathyroid adenoma was removed, which resulted in the achievement of normocalcemia.

CONCLUSION

Diabetic patients should be evaluated for hyperparathyroidism as associated hypertension can complicate the course of the disease. These patients should be evaluated for primary hyperparathyroidism when they exhibit persistent hypercalcemia and when clinical suspicion is aroused even if the serum PTH levels are within the normal range.

Very low or undetectable intact parathyroid hormone levels in patients with surgically verified parathyroid adenomas

OBJECTIVES

To report and explore potential reasons for undetectable or low-normal serum intact PTH levels in patients with surgically verified primary hyperparathyroidism with parathyroid adenomas, review the relevant literature, and offer suggestions for management of such patients occasionally encountered in clinical practice. For future research, to help understand mechanisms underlying 'undetectable' or inappropriately low serum intact PTH levels.

METHODS

Serum intact PTH levels were measured pre- and postoperatively by immunochemiluminescent assay (ICMA) and the results were confirmed by at least two repeated measurements on different occasions in each patient.

PATIENTS

We encountered two unusual patients with primary hyperparathyroidism who had suggestive biochemical and/or clinical features of primary hyperparathyroidism. However, serum intact PTH levels were either very low or undetectable in the context of hypercalcaemia, with no other obvious cause. A (99m)Tc sestamibi scan showed increased uptake in one of the parathyroid glands, suggesting a single adenoma in each case that was confirmed at surgery.

RESULTS

In the first patient, from India, mean +/- SD serum calcium was 2.6 +/- 0.32 mmol/l (reference range 2.12-2.74 mmol/l) with intact PTH of 0.11 pmol/l (reference range 1.1-7.59 pmol/l). In the second patient, from the USA, mean +/- SD serum calcium and intact PTH were 2.9 +/- 0.07 mmol/l (reference range 2.17-2.51 mmol/l) and 1.35 pmol/l (reference range 1.1-7.59 pmol/l), respectively. Following curative parathyroidectomy, serum calcium levels normalized in both patients. By contrast, serum intact PTH levels, which were either suppressed or very low before surgery, rose into the low-normal reference range in all patients.

CONCLUSIONS

When the clinical suspicion is high, the diagnosis of primary hyperparathyroidism should be pursued despite suppressed or low-normal serum intact PTH levels after carefully excluding other causes of hypercalcaemia. Further research on various intact PTH molecular species secreted by parathyroid adenomas or post-translational changes in the intact PTH molecule that might interfere with in vitro measurements should be undertaken to understand the precise reason(s) for such anomalous findings.

Understanding hypercalcemia. Its metabolic basis, signs, and symptoms

Effective diagnostic and therapeutic strategies for patients with elevated serum calcium concentrations require a thorough understanding of normal calcium metabolism and how it may be disrupted by disease.