IMAGING NEGATIVE PARATHYROID ADENOMA

Primary hyperparathyroidism typically presents with skeletal and renal manifestations. In most (80–85%) cases, the cause is a single parathyroid adenoma. We present a case of 36-year-old lady of primary hyperparathyroidism presented with multiple fractures, nephrolithiasis, and nephrocalcinosis. All of the imaging techniques to localize the cause were negative. She underwent surgical neck exploration with detection of left parathyroid adenoma. Her post-operative period was uneventful with significant clinical and biochemical improvement. Keyword: Primary hyperparathyroidism, hyperparathyroidism, hypercalcemia, parathyroid


Case Report
A 36-years-old lady was incidentally diagnosed as case of nephrolithiasis, nephrocalcinosis and right ureteric calculus which was confirmed by intravenous urography (IVU) on 17 th September during her hospital stay for treatment of fibroid uterus.Ureterolithotomy was done and chemical analysis of the stone revealed oxalate stone.Subsequently after 2-3 months she started passing of stone per urethra and she also complaints of progressively increasing generalized bodyache associated with bone pain.For these complaints she was investigated and diagnosed as a case of primary hyperparathyroidism based on raised PTH, raised calcium and decreased phosphate.Further investigations including CT, MRI of the neck and parathyroid scan were unremarkable.

Discussion:
Primary Hyperparathyroidism (PHPT) is present in about 1% of the adult population.Incidence increases to 2% or higher after age 55 years and is 2 to 3 times more common in women than in men.In India the average age at presentation is 30-40 years.
The clinical features of PHPT are mainly due to the direct and indirect effects of excess PTH on the skeleton, kidneys, and intestine and normally include bone resorption of calcium and phosphorus, enhanced intestinal absorption of calcium, renal tubular reabsorption of calcium, and hypercalciuria, resulting hypercalcaemia and hypophosphataemia.Most patients with PHPT are asymptomatic.Symptomatic patients may present with history of renal calculi, bone pain, pathologic fractures, bone shaft tumors, proximal muscle weakness (especially of the lower extremities), or nonspecific symptoms such as depression, lethargy, and vague aches and pains.
Immunoassay of the intact PTH molecule is the preferred method of measurement.This diagnosis should be suspected in symptomatic patients (typically with renal calculi, renal dysfunction, osteopenia, or osteoporosis) who have minimally increased PTH levels and high-normal serum calcium levels (normocalcemic PHPT) or intermittently increased serum calcium levels (intermittent PHPT).Dual-energy x-ray absorptiometry (DXA) scan is necessary for screening and monitoring of osteopenia and osteoporosis.
Parathyroid imaging has minimum role in the diagnosis of PHPT; the thalium-technetium subtraction method gave a sensitivity of only 73%, which compares favorably with the sensitivities of 76% for CT scanning, 55% for high resolution ultrasonography and 50-93% for magnetic resonance imaging. 11,12Combination of CT scanning and radionuclide imaging achieved a sensitivity of 90% and the combination of radionuclide imaging and ultrasound, 85%. 13rathyroidectomy is indicated in patients who meet some of the following criteria: (1) age <50 years; (2) serum calcium concentrations >1.0 mg/dl above the  Considering the clinical diagnosis of primary hyperparathyroidism, she was referred to endocrine surgeon.On surgical exploration an enlarged left superior parathyroid gland measuring 4mm×0.5 mm was identified and was removed.Histopathological examination of the excised gland revealed a benign tumor composed of polygonal cells arranged diffusely and in follicular pattern.The individual cells show abundant eosinophilic cytoplasm and small round nuclei suggestive of parathyroid adenoma.The post operative period was uneventful and her serum calcium levels returned to normal.upper limit of normal; (3) 24 h urinary calcium >400 mg; (4) creatinine clearance reduced by 30%; (5)  reduced bone mineral density (BMD; T score <-2.5) at any site.Open parathyroidectomy is the treatment of choice in PHP.
Several drugs have been used in the medical management of PHP.These can be categorized into two groups: (1) agents that act directly on PTH secretion at parathyroid cell level i.e.Calcimimetics, in particular cinacalcet; (2) those that act on PTH target organs, mainly at bone level i.e. antiresorptive drugs, such as bisphosphonates, estrogens and selective estrogen-receptor modulators (SERMs).

Conclusion
High clinical suspicion with biochemical support is essential for early diagnosis and prevention of complications of primary hyperparathyroidism.Imaging study may not help in the localization of the adenoma.Neck exploration by an expert surgeon can identify a parathyroid adenoma per-operatively.Removal of the pathological parathyroid tissue is the main therapeutic target in the management of PHP.Surgical treatment is considered the treatment of choice because it is associated with a high success rate with minimal surgical complications.