Improvements in parathyroid surgery in the intact 1-84 PTH assay era

Are biochemical values predictive of adenoma's weight in primary hyperparathyroidism?

BACKGROUND

Preoperative laboratory findings may carry some predictive value about the size of the abnormal parathyroid tissue that needs to be removed in primary hyperparathyroidism.

METHODS

In a retrospective study from 1988 to 2003, records of 71 patients with parathyroid adenoma were reviewed. The correlation between preoperative serum calcium, phosphate and parathyroid hormone (PTH) with adenoma's weight was analysed separately.

RESULTS

There was a significant correlation between preoperative serum PTH and calcium with adenoma's weight (P < 0.001 and P = 0.03, respectively). The correlation between preoperative serum phosphate and adenoma's weight was not significant (P = 0.1).

CONCLUSION

Preoperative PTH level cannot be used as a definite guide to the parathyroid adenoma's weight. Large parathyroid adenomas seem to secrete less PTH per unit weight than small adenomas. Calcium and phosphate do not seem to be of much value in predicting adenoma's weight in primary hyperparathyroidism.

Reelevation of parathyroid hormone level after parathyroidectomy in patients with primary hyperparathyroidism: importance of decreased renal parathyroid hormone sensitivity

BACKGROUND

We hypothesized that impaired peripheral sensitivity to parathyroid hormone (PTH) may play a role in reelevation of PTH after successful operation for primary hyperparathyroidism (pHPT).

METHODS

Factors affecting reelevation of PTH were determined in 90 patients who underwent parathyroidectomy for pHPT. PTH/nephrogenous cyclic adenosine monophosphate ratio, as an index of renal resistance to PTH, was examined in relation to factors shown to influence reelevation of PTH.

RESULTS

Serum PTH levels were elevated above the upper limit of normal in 23 patients (26%) at 1 week and in 39 patients (43%) at 1 month after parathyroidectomy. These 39 normocalcemic patients with elevated serum PTH at 1 month after parathyroidectomy had a higher preoperative serum level of PTH and lower serum phosphate and 25-hydroxyvitamin D (25OHD) concentrations than those with normal PTH (n = 59). Elevated PTH and low 25OHD were shown by multivariate analysis to be significant predictors of reelevation of PTH. Renal resistance to PTH was higher in patients with vitamin D deficiency or renal insufficiency than in patients with normal serum vitamin D concentrations or normal renal function, and it increased according to increases in levels of PTH.

CONCLUSIONS

The mechanism of PTH reelevation in patients with pHPT after successful parathyroidectomy appears to be renal resistance to PTH.

Hyperparathyroïdie et ostéoporose

INTRODUCTION

In patients with primary hyperparathyroidism, a definite diagnosis is the first step in the management strategy and relies on appropriately selected and carefully interpreted laboratory tests. Parathyroid hormone assays are being increasingly performed as part of the routine evaluation of osteoporosis.

CURRENT KNOWLEDGE AND KEY POINTS

In this setting, laboratory tests are often consistent with primary hyperparathyroidism but should be interpreted with caution.

FUTURE PERSPECTIVES

Bone mineral density measurements are useful for assessing the impact of primary hyperparathyroidism. The recommended bone mineral density cutoffs for selecting patients requiring parathyroidectomy were lowered in 2003, and the number of surgically treated patients has increased as a result. Parathyroidectomy remains the treatment of choice given the low mortality associated with this procedure and the absence of pharmacological alternatives suitable for long-term use.

Primary hyperparathyroidism and osteoporosis in 2004

In patients with primary hyperparathyroidism, a definite diagnosis is the first step in the management strategy and relies on appropriately selected and carefully interpreted laboratory tests. Parathyroid hormone assays are being increasingly performed as part of the routine evaluation of osteoporosis. In this setting, laboratory tests are often consistent with primary hyperparathyroidism but should be interpreted with caution. Bone mineral density measurements are useful for assessing the impact of primary hyperparathyroidism. The recommended bone mineral density cutoffs for selecting patients requiring parathyroidectomy were lowered in 2003, and the number of surgically treated patients has increased as a result. Parathyroidectomy remains the treatment of choice given the low mortality associated with this procedure and the absence of pharmacological alternatives suitable for long-term use.

The predictive value of laboratory findings in patients with primary hyperparathyroidism

BACKGROUND

Despite extensive preoperative imaging and intraoperative "gadgetry" to facilitate localization of abnormal parathyroid glands, the onus of identification and resection remains with the surgeon in the operating room. We pondered the relative usefulness of routine laboratory studies to the surgeon as predictive guides to the intraoperative findings in patients with primary hyperparathyroidism (HPT).

STUDY DESIGN

Pre- and postoperative laboratory data were analyzed in 166 consecutive patients (1998 to 1999) undergoing successful cervical exploration for sporadic primary HPT and were correlated with the pathologic findings. Patients with secondary HPT, multiple endocrine neoplasia, familial HPT, and parathyroid carcinoma were not included in this study.

RESULTS

One hundred eighteen women and 48 men (mean age = 63 years) with parathyroid adenoma (n = 155) and sporadic hyperplasia (n = 11) were evaluated. Mean parathormone (PTH) levels varied little with the pathology: adenoma = 9.6 pmol/L and hyperplasia = 10.2 pmol/L (p > 0.05). In patients with parathyroid adenoma, analysis of preoperative measures showed a positive correlation (r = 0.48, p < 0.0001) with PTH and gland weight. The correlation appeared to be the strongest in the tails of the distribution; in 22 of 23 (96%) cases with PTH levels lower than 6 pmol/L, the offending lesion or lesions were less than 400 mg; in all six cases with PTH levels higher than 18.0 pmol/L, the abnormal gland or glands weighed more than 800 mg. PTH levels between 6 and 18 pmol/L revealed mean adenoma weight of 757 mg (median = 420 mg; range = 50 to 5,500 mg).

CONCLUSIONS

Extreme values of PTH in patients with single-gland parathyroid disease alert the surgeon to the likelihood of small or large parathyroid adenomas. Laboratory studies do not differentiate adenoma from hyperplasia, nor do they pinpoint the size of abnormal glands with moderate-range PTH values.

When and how to evaluate a patient with nephrolithiasis

Nephrolithiasis is a common disorder that afflicts up to 12% of the population and continues to be a significant cause of patient injury. Evaluation of these patients should include the assessment of their comorbidities and underlying medical conditions. Patients who form stones can undergo a streamlined evaluation. A cause can be found in more than 90% of these patients. With medical treatment, stone-recurrence rates can be decreased by 85% for calcium oxalate stone formation, which affects a large proportion of patients. Introduction of nonspecific medical therapy in uncomplicated calcium stone disease may improve the quality of life for these patients and allow utilization a simple diagnostic protocol. This is in contrast to the previous recommendations of disease-specific therapy. Because patients without complications represent the majority of those who form stones, a simplified approach greatly reduces the cost of evaluation and treatment. Underlying medical conditions, however, require disease-specific therapy. The protocol represented here should aid physicians and patients in the approach to management of stone disease. The fasting calcium-load test is not required, and the entire evaluation can be performed in an ambulatory setting in two visits. Two 24-hour urine samples should be obtained on a random and restricted diet. Patients who form calcium stones can be subdivided into those who form hypercalciuric and normocalciuric stones. Patients who form normocalciuric stones are treated with conservative measures (increased fluid intake) and potassium and magnesium citrate. Patients who form hypercalciuric stones are treated with a combination of thiazides and potassium and magnesium citrate.

Secondary hyperparathyroidism is an expected consequence of parathyroidectomy for primary hyperparathyroidism: a prospective study

BACKGROUND

Parathyroidectomy for primary hyperparathyroidism (PHPT) can cause secondary hyperparathyroidism, with increased serum parathyroid hormone (PTH) and normal or low serum calcium concentrations.

METHODS

A prospective study investigated 78 consecutive patients who underwent exploration for PHPT. Serum intact PTH and total calcium concentrations were measured the evening after operation and ionized Ca++ the following morning. These levels were reassayed 1 week later.

RESULTS

Before operation, the mean PTH level was 138 +/- 15 pg/mL, total calcium concentration was 11.6 +/- 0.1 mg/dL, and ionized Ca++ concentration was 1.44 +/- 0.02 mmol/L. On the night of the operation, the PTH level was 11 +/- 2 pg/mL, and the total calcium concentration was 8.9 +/- 0.1 mg/dL. Fifty-five patients had hypoparathyroidism, with a PTH level less than 10 pg/mL. The day after the operation, the ionized Ca++ level was 1.14 +/- 0.01 mmol/L. One week later, PTH, ionized Ca++, and total serum calcium concentrations returned to normal levels. In 9 patients (12%), PTH levels were increased (98 +/- 16 pg/mL), although ionized Ca++ concentrations were normal (1.18 +/- 0.02 mmol/L), demonstrating secondary hyperparathyroidism. Risk factors for postoperative secondary hyperparathyroidism included older age, symptomatic hyperparathyroidism, higher preoperative PTH and alakaline phosphatase levels, and lower serum phosphorous levels. In 70% of these patients, PTH levels returned to normal in 3 to 12 months.

CONCLUSIONS

Secondary hyperparathyroidism occurs in 12% of patients after surgical treatment of PHPT. It is transient, possibly compensating for relative hypocalcemia.