High phosphate level directly stimulates parathyroid hormone secretion and synthesis by human parathyroid tissue in vitro

Phosphate retention plays an important role in the pathogenesis of secondary hyperparathyroidism in patients with renal failure. In in vitro studies, high extracellular phosphate levels directly stimulate PTH secretion in rat and bovine parathyroid tissue. The present study evaluates the effect of high phosphate levels on the secretion of PTH and the production of prepro PTH mRNA in human hyperplastic parathyroid glands. The study includes parathyroid glands obtained from patients with primary adenomas and from hemodialysis and kidney-transplant patients with diffuse and nodular secondary hyperplasia. The experiments were performed in vitro using small pieces of parathyroid tissue. The ability of high calcium levels to decrease PTH secretion was less in adenomas than in secondary hyperplasia; among the secondary hyperplasia, nodular was less responsive to an increase in calcium than diffuse hyperplasia. In diffuse hyperplasia, PTH secretion was increased in response to 3 and 4 mM phosphate compared with 2 mM phosphate, despite a high calcium concentration in the medium; prepro PTH mRNA levels increased after incubation in 4 mM phosphate. Similar results were obtained with nodular hyperplasia, except that the elevation of PTH secretion in response to 3 mM phosphate did not attain statistical significance. In adenomas, high calcium concentrations (1.5 mM) did not result in inhibition of PTH secretion, independent of the phosphate concentration, and the prepro PTH mRNA was not significantly increased by high phosphate levels. In conclusion, first, the PTH secretory response to an increase in calcium concentration is less in nodular than diffuse hyperplasia; second, high phosphate levels directly affect PTH secretion and gene expression in patients with advanced secondary hyperparathyroidism.     

Secondary hyperparathyroidism: comparison of clinical findings with the degree of early parathyroid hyperplasia (author's transl)

Among 580 consecutive nonselected necropsies there were 145 cases of secondary hyperparathyroidism. In 74 instances blood concentrations of Ca2+, PO4(3-), urea, creatinine, total protein, albumin and alkaline phosphatase were available for comparison with the histomorpholgical degree of parathyroid hyperplasia matched with a control group of 32 patients with normal parathyroids. Analysis of variance revealed a significant difference in the levels of PO4 (3-) and creatinine between the normal group and that with minimal hyperplasia. Minimal and moderate diffuse parathyroid hyperplasia was associated with significant difference in calcium, phosphate, urea, creatinine, and total protein concentrations.     

Primary diffuse microscopical hyperplasia of the parathyroid glands: surgical importance

In two of 182 patients with verified primary hyperparathyroidism, microscopical hyperplasia was present in all parathyroid glands that were normal in size or only slightly enlarged. All parathyroid glands in another two patients showed microscopical hyperplasia and varied from a normal size of 190 mg. In seven additional patients, microscopical hyperplasia was present in one, several, or all parathyroid glands, which varied in weight from normal to 350 mg. Familial hyperparathyroidism or multiple endocrine neoplasia was evident in five of 11 patients. Contributing to difficulties was the experience in five patients in whom removal of mildly enlarged parathyroid glands corrected hypercalcemia, but definite microscopical abnormalities were not evident by routine histologic study of the glands. Thus, there appears to be a spectrum of abnormalities relative to size and microscopical changes in parathyroid glands of patients with primary hyperparathyroidism. The surgeon should be aware of these patterns of parathyroid hyperplasia that require a search for a fifth parathyroid gland and a subtotal parathyroidectomy.     

Analysis of proliferative activity of the parathyroid glands using proliferating cell nuclear antigen in patients with hyperparathyroidism

To elucidate the cellular proliferative kinetics of the parathyroidal gland in patients with hyperparathyroidism, we investigated the expression of proliferating cell nuclear antigen (PCNA) in parathyroidal tissues using an immunohistochemical procedure. The PCNA labeling index (LI; maximum LI, maximal stained area; average LI, evenly distributed stained area) indicating cellular proliferative activity was defined as the number of PCNA-positive cells per 1000 parathyroid cells in the region of interest. We used these indexes to compare and investigate the proliferative activity of parathyroid cells under various conditions. The specimens used for the study were 42 parathyroid glands from 21 patients with primary hyperparathyroidism (19 cases of adenoma and 2 cases of primary hyperplasia due to multiple endocrine neoplasia type 1) and 129 parathyroid glands from 32 patients with secondary hyperparathyroidism. An additional 40 parathyroid glands resected during thyroid surgery of 30 normocalcemic patients were used as normal controls. In normally functioning parathyroids, a small number of cells in the growth phase were found. In primary hyperparathyroidism, proliferative activity was highest in the adenoma followed by primary hyperplasia. In contrast, the PCNA LIs showed a low value in the normal rim of the adenoma and normal glands resected as biopsy specimens from adenoma patients. We, therefore, assumed that proliferative activity was suppressed in these cells compared with that in normally functioning glands. In secondary hyperparathyroidism, when the cell component of the parathyroid tissues was divided into five types, PCNA immunoreactivity was lowest in the dark chief cells. Proliferative activity in cells of the oxyphil series was the same or higher than that in the clear chief cells or vacuolated chief cells. When classified according to the structure of the parathyroid glands, cell proliferation was significantly higher in the nodular type than in the diffuse type (maximum LI, 176 +/- 231 vs. 38.3 +/- 55.7; average LI, 120 +/- 188 vs. 24.8 +/- 43.5; mean +/- SD; P < 0.001). More PCNA-immunoreactive cells were found in autotransplanted glands with recurrence than in glands resected during the initial surgery. To summarize the PCNA expression classified according to the pathological types of hyperparathyroidism, the PCNA LIs were highest in secondary hyperplasia (maximum LI, 144 +/- 212; average LI, 96.0 +/- 169) and adenoma (maximum LI, 102 +/- 81.7; average LI, 67.5 +/- 67.7), followed by primary hyperplasia (maximum LI, 25.0 +/- 25.4; average LI, 19.2 +/- 22.2) and normal glands (maximum LI, 13.6 +/- 23.9; average LI, 4.40 +/- 8.90). These findings suggest that the cellular proliferative kinetics of the parathyroid gland differ depending on the type of hyperparathyroidism, glandular structure, and cell components. As the detection method of intranuclear expression of PCNA in cells is too sensitive, we should be careful not to overestimate the number of cells in the proliferative cycle. However, these results could not have been obtained using a conventional method such as DNA analysis by flow cytometry.     

Short- and long-term efficacy of total parathyroidectomy with immediate autografting compared with subtotal parathyroidectomy in hemodialysis patients

A retrospective study was performed in chronic hemodialysis patients comparing total parathyroidectomy (PTX) followed by immediate autografting (IA) (total PTX+IA) with subtotal parathyroidectomy (subtotal PTX). One hundred six patients with severe, uncontrolled hyperparathyroidism were referred to this center and underwent surgery during the period from 1980 to 1990. Long-term follow-up after PTX was available in 49 of them: 28 patients had total PTX+IA and 21 had subtotal PTX. The two surgical methods were evaluated with respect to preoperative severity of hyperparathyroidism, immediate postoperative results, and long-term parathyroid status, as evaluated by an RIA measuring intact immunoreactive parathyroid hormone (intact iPTH; normal values, 15 to 65 pg/mL). The initial degree of hyperparathyroidism was comparable in the two groups. An excellent short-term control of hyperparathyroidism was achieved in the great majority (95%) of patients with either surgical procedure. However, long-term normalization of parathyroid gland activity was achieved in only one third of patients whereas 33% had elevated intact iPTH levels (> 130 pg/mL; i.e., higher than twice the upper range of normal) and 32% had low intact iPTH levels (< 15 pg/mL), consistent with permanent hypoparathyroidism. No difference was found in the immediate failure rates: 0 of 28 cases after total PTX+IA compared with 2 of 21 cases after subtotal PTX. Similarly, long-term intact iPTH levels were comparable: 400 +/- 105 versus 212 +/- 82 pg/mL (mean +/- SE; P = not significant). Interestingly, long-term serum intact iPTH levels were higher in patients with nodular (N = 18) than with diffusely (N = 26) hyperplastic glands: 556 +/- 146 versus 126 +/- 52 pg/mL (P < 0.001) and recurrence of hyperparathyroidism was more frequent with nodular hyperplasia (11 of 18) than with diffuse hyperplasia (4 of 26) (P < 0.02). In conclusion, although excellent short-term results were obtained with both procedures, satisfactory long-term control of parathyroid gland function was achieved in only one third of the patients, the other two third remaining either hypoparathyroid or developing recurrent hyperparathyroidism. Last, the histological subtype of parathyroid glands was partially predictive of the recurrence of hyperparathyroidism.     

Tertiary hyperparathyroidism after renal transplantation: surgical strategy

BACKGROUND: An analysis of our experience with tertiary hyperparathyroidism (III HPT) in renal transplantations between 1981 and 1996 was reviewed to examine a variety of laboratory and clinical variables in this population. METHODS: A total of 3233 kidney transplantations were performed; 48 patients underwent parathyroidectomy for III HPT. Five patients were excluded from analysis due to the development of renal dysfunction. The index 43 patients were divided into two groups. Group I consisted of 31 patients (72%) with either enlargement of all parathyroid glands (n = 26) or 3/4 gland enlargement (n = 5). These patients were assumed to have hyperplasia and underwent subtotal parathyroidectomy or total parathyroidectomy. Group II consisted of 12 patients (28%) with single (7/12; 58%) or two-gland enlargement (5/12; 42%). Group II patients underwent resection of only the enlarged glands. RESULTS: Laboratory and clinical parameters showed no difference between the groups during long-term follow-up. Most patients in groups I and II were eucalcemic after parathyroidectomy. However, postoperative hypercalcemia and hypocalcemia did occur in group I (mean postoperative calcium: group I = 9.29 +/- 0.63 mg/dL; group II = 9.42 +/- 0.58 mg/dL). CONCLUSIONS: Four gland parathyroid enlargement is a frequent finding in III HPT, although asymmetric enlargement can occur. Histologically, this represents sporadic adenomas and asymmetric hyperplasia. Intraoperative findings should dictate surgical strategy; with asymmetric enlargement only the enlarged parathyroid glands should be resected.     

Parathyroid scintigraphy with Tc99m Sestamibi

BACKGROUND: Parathyroid scintigraphy with Tc99m Sestamibi, a tracer that is taken up by hyperfunctioning parathyroid tissue, has a high yield in the diagnosis of abnormal parathyroid growths. AIM: To assess the usefulness of parathyroid scintigraphy with Tc99m Sestamibi in patients with suspected hyperparathyroidism. PATIENTS AND METHODS: We analyzed retrospectively 29 patients with suspected hyperparathyroidism, in whom a scintigraphy with Tc99m Sestamibi was performed. RESULTS: Twenty four of 25 patients in whom hyperfunctioning parathyroid tissue was evidenced with scintigraphy, were operated. Histological diagnosis of the excised parathyroid gland, showed 23 adenomas and 1 hyperplasia. Anatomical location disclosed by scintigraphy was concordant with surgical findings in all cases, including a mediastinic adenoma. Of the four patients with negative scintigraphic findings, two had transitory PTH elevations and in two the presence of adenoma or hyperplasia could not be demonstrated with other diagnostic procedures. CONCLUSIONS: Parathyroid scintigraphy with Tc99m Sestamibi had an 86% sensitivity for the detection of hyperfunctioning parathyroid tissue in patients with elevated PTH.     

Parathyroid hyperplasia in primary hyperparathyroidism: a review of 85 cases

Parathyroid hyperplasia of all four glands was found to be the cause of primary hyperparathyroidism in 85 of 557 cases seen at the Massachusetts General Hospital between 1930 and 1973. There were 66 cases of chief cell hyperplasia and 19 cases of clear cell hyperplasia that were grossly, microscopically, and ultrastructurally distinct. Although the clinical findings overlap, there are several differences in the signs and symptoms between these two forms of hyperplasia. Both types are treated by subtotal removal of all the parathyroid tissue. Removal of insufficient tissue has left residual hyperparathyroidism in 45% of those with chief cell hyperplasia and 11% of those with clear cell hyperplasia after what was thought to be definitive surgery. Postoperative hypoparathyroidism was found in 15% of the patients with chief cell hyperplasia and in none with clear cell hyperplasia. These findings further suggest that removal of three and one-half glands in the more than 86% of patients with one gland involvement (adenoma or carcinoma) as the cause of primary hyperparathyroidism is unwarranted.     

Intrathyroidal parathyroid glands can be a cause of failed cervical exploration for hyperparathyroidism

BACKGROUND: The incidence of intrathyroidal parathyroid glands remains controversial. The purpose of this study was to determine the incidence in a series of patients with hyperparathyroidism. METHODS: Three hundred nine patients underwent parathyroidectomy. Patients were divided into two groups: uniglandular disease versus hyperplasia. RESULTS: Eighteen of 309 patients (6%) had abnormal intrathyroidal parathyroid glands. The incidence was 3% (7 of 222) in patients with uniglandular disease versus 15% (11 of 73) in those with hyperplasia. With a mean follow-up of 54 months, 12 patients are eucalcemic, 5 have persistent hypocalcemia, and 1 has recurrent hypercalcemia. There were no recurrent laryngeal nerve injuries. CONCLUSIONS: These data suggest that an intrathyroidal adenoma is an uncommon cause of failure, whereas abnormal intrathyroidal parathyroid tissue may be a more common cause of failure in patients with hyperplasia.     

Targeted ablation of the vitamin D receptor: an animal model of vitamin D-dependent rickets type II with alopecia

Vitamin D, the major steroid hormone that controls mineral ion homeostasis, exerts its actions through the vitamin D receptor (VDR). The VDR is expressed in many tissues, including several tissues not thought to play a role in mineral metabolism. Studies in kindreds with VDR mutations (vitamin D-dependent rickets type II, VDDR II) have demonstrated hypocalcemia, hyperparathyroidism, rickets, and osteomalacia. Alopecia, which is not a feature of vitamin D deficiency, is seen in some kindreds. We have generated a mouse model of VDDR II by targeted ablation of the second zinc finger of the VDR DNA-binding domain. Despite known expression of the VDR in fetal life, homozygous mice are phenotypically normal at birth and demonstrate normal survival at least until 6 months. They become hypocalcemic at 21 days of age, at which time their parathyroid hormone (PTH) levels begin to rise. Hyperparathyroidism is accompanied by an increase in the size of the parathyroid gland as well as an increase in PTH mRNA levels. Rickets and osteomalacia are seen by day 35; however, as early as day 15, there is an expansion in the zone of hypertrophic chondrocytes in the growth plate. In contrast to animals made vitamin D deficient by dietary means, and like some patients with VDDR II, these mice develop progressive alopecia from the age of 4 weeks.     

Direct cloning of human parathyroid hyperplasia cells in soft-agar culture

Parathyroid specimens removed from patients with clinical hyperparathyroidism were cultured in a two-layer soft-agar system. Four patients had parathyroid hyperplasia and one had a parathyroid adenoma. Colonies grew from single-cell suspensions of each specimen. Plating efficiency ranged from 0.001 to 0.05%. No colonies grew from normal bovine parathyroid specimens. Parathormone was detected in 0.9% NaCl solution incubated with the culture plates of three of the four human specimens tested. Parathormone levels determined by radioimmunoassay ranged from 10.4 < 100 ng/ml. Plates tested serially showed a progressive rise in parathormone levels with time and an increase in colony size and number. Microscopic evaluation of the cellular layer showed clusters of cells morphologically consistent with parathyroid origin. Colonies remained viable for approximately 3 weeks. These data confirm that malignancy of tissue in vivo is not necessary for colony formation in agar and that human parathyroid hyperplasia or adenoma cells produce and secrete parathormone in this system.     

Parathyroid detection in secondary hyperparathyroidism with 123I/99mTc-sestamibi subtraction single photon emission computed tomography

123I/99mTc-sestamibi subtraction single photon emission computed tomography (SPECT) has been proposed to detect hyperplastic parathyroid tissue, but the clinical usefulness of this technique in secondary hyperparathyroidism is uncertain. The purpose of this study was to evaluate preoperative parathyroid localization using 123I/99mTc-sestamibi subtraction SPECT in patients with renal failure and secondary hyperparathyroidism. Nineteen patients with chronic renal failure and secondary hyperparathyroidism underwent 123I/99mTc-sestamibi subtraction SPECT imaging preoperatively. None of these patients had undergone previous neck surgery. The location, weight, and histopathological results of all identified parathyroid glands were recorded. Surgery was considered successful in all patients, with resection of a total of 74 hyperplastic parathyroid glands. 123I/99mTc-sestamibi subtraction SPECT correctly identified 57 of these parathyroid glands (77% sensitivity). The mean weight among the true positive glands (n = 57) was 1031 mg (range, 45-7900 mg), and that among the false negative glands (n = 17) was 465 mg (range, 20-1800 mg). This difference between the mean weights was statistically significant (P = 0.018). There was a positive correlation between parathyroid weight and detectability with 123I/99mTc-sestamibi subtraction SPECT (Spearman correlation = 0.28; P = 0.0167). 123I/99mTc-sestamibi subtraction SPECT is able to correctly localize hyperplastic parathyroid glands in patients with renal failure and secondary hyperparathyroidism, but there is a fairly weak relationship between preoperative detection rate and anatomical parathyroid gland size.     

Value of ultrasonography, CT and MR imaging in the diagnosis of primary hyperparathyroidism

PURPOSE: To evaluate the significance of preoperative localization of abnormal parathyroid glands to the surgical outcome in patients with primary hyperparathyroidism. MATERIAL AND METHODS: Thirty-nine patients with primary hyperparathyroidism were studied preoperatively with US (39 patients), CT (30 patients) and MR imaging (18 patients). The overall diagnostic accuracy for US was 87%, CT 66% and MR 94%. In patients with a single parathyroid adenoma US was the most cost-effective localization technique with a detection rate of 96%. CT had a lower detection rate (78%) but was of particular value for fairly large ectopic adenomas in the root of the neck. MR imaging was a good confirmatory test (93%). In patients with multiple gland disease (primary hyperplasia and multiple adenomas), no single localization study alone was sufficient. Combination of all 3 studies, however, alerted the physician to the presence of disease in more than one gland in 87% of these patients. CONCLUSION: US, CT and MR imaging followed by surgery performed by an experienced surgeon provided good clinical results in 39 patients with primary hyperparathyroidism. Preoperative localization was especially useful in patients with primary parathyroid hyperplasia or multiple adenomas and in patients with ectopic parathyroid adenomas in the root of the neck. We recommend identification of all abnormal parathyroid glands prior to surgery.