Normocalcaemic hyperparathyroidism after parathyroidectomy: A retrospective study

The role of parathyroid hormone measurements after surgery for primary hyperparathyroidism

BACKGROUND

During parathyroidectomy for primary hyperparathyroidism (pHPT), intraoperative parathyroid hormone (IOPTH) levels are used to confirm removal of all hyperfunctioning parathyroid tissue. The phenomenon of elevated parathyroid hormone (PTH) levels with normocalcemia after curative parathyroidectomy, seen in up to 40% of patients, continues to be an unexpected and unexplained finding. We therefore investigated whether postoperative PTH levels are as reliable as IOPTH levels in predicting cure after surgery for pHPT.

METHODS

We reviewed our prospective database of consecutive patients undergoing surgery for pHPT between December 1999 and November 2004. Curative parathyroidectomy was defined as normocalcemia 6 months or longer postoperatively.

RESULTS

A total of 328 patients who underwent 330 operations for pHPT had IOPTH measurements and serum follow-up calcium levels at 6 months or longer. Surgery was curative in 315 (95.5%) operations. IOPTH levels correctly predicted operative success in 98.2% (positive predictive value [PPV]. Postoperatively, the PPV of a normal PTH level at 1 week, 3 months, and 6 months was 97.1%, 97.3%, and 96.5%, respectively. Of all patients with an elevated postoperative PTH level at 1 week, 3 months, or 6 months, only 13.7%, 14.3%, and 14%, respectively, were not cured.

CONCLUSIONS

Normal postoperative PTH levels reliably predict operative success. However, they do not improve upon results predicted by IOPTH levels. Elevated postoperative PTH levels do not predict operative failure in most patients. We propose that PTH measurements after surgery for pHPT may be misleading, costly, and not indicated in normocalcemic patients.

SOME CHARACTERISTICS OF PRIMARY HYPERPARATHYROIDISM IN VIETNAMESE IMMIGRANTS LIVING IN SOUTHERN CALIFORNIA

OBJECTIVE

To characterize primary hyperparathyroidism (PHP) in Vietnamese immigrants living in southern California and to summarize the results of treatment.

METHODS

We describe 11 patients (8 women and 3 men) with a mean age of 57.91 years who underwent follow-up from 1991 to 1995 after PHP was diagnosed. The patients had no specific complaints. Four patients had a history of kidney stones, and five had chronic hypertension. Only five patients had high levels of total serum calcium; the other six patients had normal or fluctuating levels of total serum calcium. All patients, however, had high levels of intact parathyroid hormone (PTH) and ionized calcium. Preoperatively, parathyroid imaging with technetium-99m sestamibi demonstrated persistently increased parathyroid gland uptake.

RESULTS

In all nine patients who underwent surgical treatment, an adenoma was found in the parathyroid glands; two patients refused operative intervention. The mean serum phosphate was in the low-normal range and increased postoperatively (2.70 versus 3.52 mg/dL; P<0.001). The mean serum chloride level also decreased postoperatively (104.62 versus 100.78 mEq/L; P<0.001). The ratio of chloride/phosphate decreased significantly after adenoma removal (39.44 versus 29.21; P<0.001). Six patients received calcium gluconate either alone or in combination with vitamin D supplements for hypocalcemia postoperatively. The other three patients, however--who did not receive calcium supplements postoperatively--had persistently high levels of intact PTH but normal serum Ca++ levels and subsequently were treated effectively with calcium gluconate and vitamin D.

CONCLUSION

The presence of hypercalcemia, especially Ca++, and an increased level of intact PTH establishes the diagnosis of PHP. After parathyroidectomy, the persistence of high levels of intact PTH in association with normal serum Ca++ suggested the presence of secondary hyperparathyroidism, which was treated effectively with calcium gluconate and vitamin D. These patients had the same clinical picture as other ethnic groups with PHP, but they needed either calcium alone or calcium and vitamin D supplements after parathyroidectomy because of their bone loss from prolonged PHP.

The cause of maintained hypercalciuria after the surgical cure of primary hyperparathyroidism is a defect in renal calcium reabsorption

The hypercalciuria that eventually remains after the successful removal of a solitary parathyroid adenoma may originate from excessive intestinal calcium absorption, bone resorption or deficient renal reabsorption. In order to clarify this question, ten patients surgically cured from primary hyperparathyroidism (PHPx), ten age-matched normal subjects and five nephrolithiasic patients with renal hypercalciuria (RH) were studied after five days on a low calcium diet, either during fasting or after oral calcium load. Fasting serum calcium, amino-terminal and intact PTH levels and also urinary cAMP excretion were normal in every individual patient. Serum ionized calcium and inulin clearance (GFR) were used for calculations of the filtered load (FL Ca) and the fractional excretion of calcium (FE Ca). Six PHPx patients displayed fasting calciuria above the upper limit calculated for control subjects, despite having the lowest GFR and FL Ca (p < 0.05 vs control). These patients (h-PHPx) had a small calciuric response to oral calcium load. Serum 1,25-(OH)2D3 and 25OHD3 did not correlate with calciuria. Our findings exclude intestinal hyperabsorption and excessive bone resorption in h-PHPx patients, and strongly suggest a renal tubular defect in calcium reabsorption as the cause of their hypercalciuria. This defect could be primary, as in RH, but only three hPHPx patients had recurrent kidney stones before surgery. On the other hand, as a negative correlation between GFR and FE Ca was only found in PHPx patients, it seems probable that the disturbances in glomerular and tubular functions were secondary to the long standing hypercalcemic hyperparathyroidism.