Pathophysiology and diagnosis of primary hyperparathyroidism--strategy for asymptomatic primary hyperparathyroidism

Elastic properties of aorta in patients with primary hyperparathyroidism

In this study, we aimed to evaluate whether hyperpara thyroidism affects the elastic properties of aorta, calculated as aortic distensibility and aortic stiffness index. Eighteen patients with hyperparathyroidism were enrolled in the study. The control group consisted of 18 healthy subjects with similar baseline characteristics. All subjects underwent echocardiographic examination. Internal aortic root diameters were measured at 3 cm above the aortic valve by the use of two-dimensional guided M-mode transthoracic echocardiography, and arterial blood pressure was measured simultaneously from the brachial artery by sphygmomano metry. Two indexes of the aortic elastic properties were measured which are aortic distensibility and aortic stiffness index. The mean aortic stiffness index of hyperparathyroidic patients was higher (3.04 +/- 1.26 vs. 2.36 +/- 1.09; p = 0.048), and aortic distensibility was lower (15.62 +/- 5.84 vs. 22.64 +/- 14.54; p = 0.035) than the control group. The left ventricular (LV) mass index (242.44 +/- 46.3 vs. 212.8 +/- 43.97; p = 0.048), although it has failed to reach statistical significance, and LV wall stress (57.81 +/- 18.22 vs. 46.57 +/- 15.72; p = 0.08) of these patients was also higher than control group. Hyperparathyroidism increases aortic stiffness index and decreases aortic distensibility of primary hyper parathyroidic patients compared with normal population. The affected aortic elastic properties can be a factor in increased LV mass index and wall stress.

Inhibition of growth hormone secretion in mild primary hyperparathyroidism

INTRODUCTION

Impairment in growth hormone (GH) secretion has been reported to occur in primary hyperparathyroidism (PHP) with strikingly elevated (>150 pg/ml) plasma PTH and free Ca levels. Patients with these characteristics are relatively few, whereas the great majority of patients with biochemically diagnosed PHP are asymptomatic and show borderline or slightly elevated plasma PTH and Ca levels. We wondered whether also patients in these latter conditions show a defective GH secretory pattern.

METHODS

In order to answer this question, 8 female subjects (mean age +/- SE: 44 +/- 1.3 years) were selected at the time of a checkup examination from a larger population of persons in fairly good clinical condition. Inclusion criteria were plasma PTH values slightly above the normal range (up to 50% higher than the maximum limit) with free Ca levels in the upper normal range or slightly higher (experimental group). Normal values in our laboratory are ionized calcium: 1.22-1.42 mmol/ml and plasma PTH: 12-72 pg/ml. A group of 15 age-matched healthy women with plasma PTH and Ca levels in the middle normal range and significantly lower than values found in the experimental group was also selected and used as control. Experimental and control groups were tested with arginine [0.5 mg/kg body weight (BW)] infused intravenously over 30 min and arginine plus GH-releasing hormone (GHRH; 1 microg/kg BW in an intravenous bolus injection). The GH responses to these challenging stimulations were compared between groups.

RESULTS

Basal serum GH values were similar in all subjects. Both arginine and arginine plus GHRH induced a significant GH rise in both groups; however, the GH responses were significantly lower in the experimental than in the control group. Mean GH peak was 27.7 and 14.6 times higher than baseline after arginine and 57.5 and 26.6 times higher than baseline after arginine plus GHRH in the control and experimental group, respectively. No significant correlation was observed between PTH or Ca levels and the GH responses to challenging stimuli in any group.

CONCLUSION

These data show that impairment in GH secretion is associated with slightly elevated levels of PTH in the presence of serum Ca values in the upper normal range. GH responses to stimulations were reduced by about 50% in our hyperparathyroid subjects. A long-time duration of this relatively small decline of GH secretory activity may be supposed to contribute to age-related catabolic processes in a large number of patients with mild primary hyperparathyroidism.

Serum N-terminal midfragment vs. intact osteocalcin immunoradiometric assay as markers for bone turnover and bone loss in hemodialysis patients

Although labile, assay of intact osteocalcin (iOC) is established as the standard assay for evaluating osteoblastic function. The present study examines the clinical usefulness of the newly developed immunoradiometric assay for osteocalcin (OC), which identifies the stable N-terminal midfragment of OC (N-MID OC assay), in hemodialysis (HD) patients. The performance of N-MID OC assay was compared to that of iOC assay in the sera obtained from 137 male HD patients, by comparing these assays with those of other bone metabolic markers and bone loss during a 1-year period before determination of serum markers. Serum N-MID OC values did not decrease significantly during 24 h incubation at room temperature, whereas serum iOC decreased significantly after 1 h incubation. Serum N-MID and iOC in the 137 male HD patients were 197.3 +/- 57.8 and 34.6 +/- 30.0 ng/ml, respectively, or 3.9 +/- 3.1 and 2.8 +/- 2.4 times above the respective reported normal upper limits. Serum N-MID OC correlated significantly in a positive manner with serum iOC (r = 0.934, P < 0.0001). Serum N-MID OC correlated no less significantly in a positive manner with serum levels of bone alkaline phosphatase, deoxypyridinoline, and intact parathyroid hormone compared to serum iOC. Of interest was the fact that serum N-MID OC, but not iOC, correlated significantly with both the amount and the rate of bone loss at the distal radius 1/3. In summary, the findings suggest that N-MID OC immunoreactivity is much more stable than iOC immunoreactivity and that N-MID OC assay may be less susceptible to the OC fragments reported to accumulate in uremic serum. It may, therefore, prove more reliable than iOC assay for evaluating bone turnover, and thus for reflecting bone loss, in HD patients.

Clinical usefulness of the serum N-terminal propeptide of type I collagen as a marker of bone formation in hemodialysis patients

BACKGROUND

An intact collagen I amino-terminal propeptide (PINP) assay has been developed as a useful assay for bone formation. The present study was performed to investigate the clinical usefulness of serum PINP as a bone-formation marker in hemodialysis (HD) patients.

METHODS

PINP and other bone-formation markers, ie, bone alkaline phosphatase (BAP) and intact osteocalcin (OC), were determined in serum samples collected from 209 HD patients.

RESULTS

Serum PINP levels, in contrast to serum BAP and OC levels, did not change significantly during a single HD session (P = 0.069; n = 14). There were significant positive correlations between serum PINP and BAP (r = 0.723; P < 0.001) and OC values (r = 0.739; P < 0.001), as well as intact parathyroid hormone (r = 0.652; P < 0.001) and bone-resorption marker values: deoxypyridinoline (DPD; r = 0.823; P < 0.001), pyridinoline (PYD; r = 0.735; P < 0.001), and beta-crosslaps (r = 0.705; P < 0.001). Serum PINP values correlated significantly more strongly than serum BAP values with all bone-resorption markers. Serum PINP values significantly correlated negatively with annual changes in bone mineral density (BMD) in the distal third of the radius (r = -0.286; P < 0.001). When subjects were divided into tertiles according to degree of bone loss, subjects with greater bone loss had significantly greater serum PINP, BAP, and OC levels, although PINP and OC provided greater discrimination than BAP. PINP-PYD and PINP-DPD ratios, indices of osteoblast function not confounded by enhanced bone resorption, significantly positively correlated with annual BMD changes in the distal third of the radius (PINP-PYD ratio, P = 0.008; PINP-DPD, P = 0.015).

CONCLUSION

Serum PINP may provide a better marker of osteoblast function in HD patients and thus be clinically useful for predicting radius bone loss.

Impaired secretion of parathyroid hormone, but not refractoriness of osteoblast, is a major mechanism of low bone turnover in hemodialyzed patients with diabetes mellitus

Diabetic bone disease is characterized by low bone turnover resulting from either impaired secretion of parathyroid hormone (PTH) or refractoriness of osteoblasts to PTH. The present study was performed to elucidate which factor contributes more to the reduction in bone turnover by comparison between 64 hemodialyzed patients with diabetes mellitus and 106 hemodialyzed patients without diabetes mellitus. Only men were enrolled to avoid the influence of the menstrual cycle on bone metabolism. Serum intact PTH (iPTH) levels were significantly lower in hemodialyzed patients with diabetes than those without diabetes, although no significant difference existed in age, duration of hemodialysis therapy, or serum calcium or phosphate levels. Of the biochemical markers measured, serum intact osteocalcin (iOC) and deoxypyridinoline levels were significantly lower in patients with diabetes, although serum bone-specific alkaline phosphatase (BAP) and pyridinoline levels did not differ significantly between the two groups of patients. When patients were restricted to those with serum iPTH levels greater than 180 pg/mL, this parameter correlated significantly in a positive manner with both serum iOC and BAP levels and negatively with bone mineral density at distal radius 1/3. Regression slopes between iPTH levels and these parameters were not significantly different between the two groups of patients, indicating the absence of refractoriness of bone to PTH in patients with diabetes. In conclusion, our findings suggest that impaired PTH secretion, but not refractoriness of osteoblasts to PTH, may be responsible for the low bone turnover in hemodialyzed patients with diabetes.

The spectrum of radiographic findings in primary hyperparathyroidism

The aim of this study was to assess the spectrum of radiographic findings in primary hyperparathyroidism (PHPT). The study group consisted of 16 women and 7 men whose Ca levels were at least two or three times higher than normal. The average age was 55.3 in women and 49.4 in men. We detected carcinoma in 1, hyperplasia in 1, multiple adenomas in 4, single adenoma in 17 patients. The most common finding in the skeletal system was the decreased bone mineral density (BMD) and the complete loss of the lamina durae dentium. BMD was found lower in women than in men. This result attributed the increased number of postmenopausal patients in our study group. The second most common finding in our study group was subperiosteal bone resorption. Brown tumors (BTs) were located at maxilla in one, widespread in one, mandibula in two, long tubular bones in four patients. Renal stone disease was found in five, spastic colon in two, gastric ulcer in one, mitral valve calcification in one patients. We demonstrated no pathologic changes consistent with PHPT in remaining seven patients.