The abnormal parathyroid

Ultrastructure of human parathyroid cells in health and disease

Parathyroid glands (n = 271) removed from 130 patients were examined by light and electron microscopy. A standardized method of tissue processing was employed and morphometry was performed. The aim of the paper is to provide a description of the human parathyroid chief cell ultrastructure in health and disease, with quantitative evaluation of structures involved in secretion of parathyroid hormone in a large case series, and to discuss their role in current diagnostic histopathology. The patients were euparathyroid (n = 10), or affected by primary (n = 97), secondary (n = 8), or tertiary (n = 15) hyperparathyroidism. In normal glands, solid parenchyma was composed of chief cells, large clear cells, transitional-oxyphil cells, and oxyphil cells. Chief cell hyperplasia, pseudo-adenomatous hyperplasia, adenoma, water-clear cell hyperplasia, and carcinoma were the most usual forms of parathyroid disease responsible for primary hyperparathyroidism. In chief cell hyperplasia, all the parathyroid glands were enlarged and the chief cells were in an active state of hormone secretion, with a large Golgi complex, abundant rough endoplasmic reticulum (RER), small lipid droplets, and tortuous plasma membrane. In pseudo-adenomatous hyperplasia, one gland was enlarged and the others displayed a normal size; however, electron microscopic examination and morphometric analysis showed that all the glands had active cells. Adenomas displayed a pattern similar to those of pseudo-adenomatous hyperplasia, with one gland enlarged and the others of normal size. However, ultrastructural examination and morphometry showed that the normal-size glands were hypo-active. Water-clear cell hyperplasia showed cells filled with cytoplasmic vacuoles. In these cells, structures with intermediate features between secretory granules and vacuoles were visible. Nucleo-cytoplasmic atypias were frequently visible in parathyroid carcinoma cells. In secondary and tertiary hyperplasia, active chief cells were regularly mixed with oxyphil or transitional-oxyphil cells. The tertiary hyperplasia was characterized by RER-associated structures that were not found in the normal or other pathological conditions. These results demonstrate that electron microscopy and morphometry represent useful tools in parathyroid histopathology.

A study of parathyroid hyperplasia in chronic renal failure

Specimens removed at parathyroidectomy from 41 patients with chronic renal failure, 12 patients with parathyroid adenomas and parathyroid glands from 24 autopsies were studied by light microscopy, immunohistochemistry and electron microscopy. The morphological abnormalities were correlated with clinical data obtained from patients' medical records. Glandular enlargement in chronic renal failure, primarily due to parenchymal cell hyperplasia, was as much as 20 times the normal in contrast to 40 times the normal cases of adenomas. Glandular hyperplasia was mostly due to an increase in the number of chief cells and to a lesser extent increase in the number of oxyphil cells, transitional oxyphil cells and water-clear cells. There was a corresponding reduction in fat and intracellular lipid content. There were differences in the overall morphology of normal, hyperplastic and adenomatous glands. The clear histological distinction between hyperplastic and adenomatous glands was at times difficult. There was no correlation between the extent of hyperplasia, the cause of renal failure, duration of chronic renal failure, levels of serum calcium, phosphate or parathyroid hormone. Immunohistochemical studies showed that all 3 types of cells contained parathyroid hormone but in hyperplastic and adenomatous glands there was a reduction in parathyroid hormone and chromogranin A staining. There were no specific ultrastructural abnormalities which would distinguish between hyperplastic and adenomatous glands.

Surgery for parathyroid adenoma and hyperplasia: relationship of histology to outcome

Recent histopathologic evidence challenges the teaching that enlargement of a solitary parathyroid gland is invariably caused by an adenoma, whereas multiple gland enlargement results from hyperplasia. We have re-examined the parathyroid tissue obtained from 152 consecutive patients undergoing surgery for primary hyperparathyroidism and compared it with their clinical outcome. Our approach was to excise enlarged glands and biopsy the remainder. In 124 patients (82%) at least three glands were biopsied or removed. The ratio of adenoma to hyperplasia was reversed by our histologic re-examination; adenomas were found in only 27 patients (25 single, two double), whereas hyperplasia was found in 117 patients (one gland, 87 patients; two glands, 16 patients; three glands, five patients; four glands, nine patients). Normal tissue only was reported in eight patients. During a 2-year follow-up, five patients (3%) developed hypocalcemia and none developed recurrent hypercalcemia. Our results indicate that a full neck exploration with removal of all enlarged glands is more important than the histologic diagnosis in planning a successful surgical strategy for primary hyperparathyroidism.

DNA analysis and parathyroid pathology

The nuclear DNA content of 85 parathyroid glands (4 carcinomas, 39 adenomas, 21 secondary parathyroid hyperplasias, and 21 normal parathyroid glands) were determined by flow cytometric analysis. All normal parathyroid glands, 85% of the adenomas, and 83.3% of the secondary hyperplastic glands had DNA indices within values of 0.85-1.1. Paraffin-embedded fixed glands showed less DNA staining than that found with fresh or normal glands. Glands from patients with carcinoma showed DNA indices outside the normal DNA index range. When the percent of nuclei within the G0/G1 phase of the cell cycle was compared between the study groups, highly significant results were found. While patients with secondary hyperplasia showed a similar distribution to the normal glands studied, only 48% of primary adenomas showed over 80% of cells within the G0/G1 region. A clear subgroup of adenomas was defined with more rapidly cycling tetraploid cells, and showing classical adenoma pathology. This group showed negative correlation with gland weight, plasma calcium, and ionized calcium. These findings suggested that a different etiology of the disease process occurs between secondary hyperplasia and parathyroid adenoma. Such abnormal adenomas may form a group worthy of long-term follow-up.

Morphometric evaluation of intracytoplasmic lipid in normal and pathological parathyroid glands

The chief morphological criterion for classifying parathyroid glands as 'normal', 'suppressed', or 'activated' is the lipid content of the cytoplasm. In particular, cytoplasm lipid deposit is scanty in the active parathyroid cell, according to many authors. In this paper we present the results of a morphometrical study of ten normal parathyroid glands from patients undergoing thyroidectomy, 20 enlarged 'adenomatous' glands from patients with primary hyperparathyroidism, and 20 glands of normal size from the same hyperparathyroid patients. We aimed at assessing the content of intracytoplasmic lipid of secretory cells in all these conditions. The results show that secretory cells of adenomatous glands have less lipid than those from normal glands; however, there was considerable overlapping of the data in the two groups. The mean lipid content of cells in glands of normal size taken from hyperparathyroid patients was not significantly different from the mean value of normal cells, even when ultrastructural evidence of activation was present in the former. These data suggest that caution has to be exercised in assessing the functional status of parathyroid glands on the basis of lipid content of secretory cells, mainly when differentiating between adenoma and hyperplasia.

Different responses between the upper and the lower parathyroid gland in a state of secondary hyperfunction. A study on chronic renal failure by morphometry and nuclear DNA analysis

The size of the parathyroid gland and the size, the numerical density and nuclear DNA-content of the parathyroid gland cells were evaluated in chronic renal failure (CRF) and revealed a difference between the upper and the lower glands in the manner of adaptation to a state of long-term hyperfunction, secondary to CRF. The parathyroid gland enlarged as a whole in CRF, an effect more marked in the lower gland, whereas individual parathyroid gland cell enlargement in CRF was mainly seen in the upper gland cells. The numerical density of the lower parathyroid gland cells was higher than that of the upper gland. Nuclear DNA-content of the parathyroid gland cells were increased in CRF and the lower gland tended to show hyperdiploid aneuploidy. These findings are probably related to the fact that parathyroid adenomas occur most often in the lower gland. The higher proliferative activity of the lower parathyroid gland in long-term hyperfunction may explain the higher risk for the lower gland in the occurrence of adenomas.

[Parathyroidectomy and autotransplantation in renal hyperparathyroidism. I. Morphologic studies for tissue selection]

During total parathyroidectomy and autotransplantation 140 enlarged glands were removed in 35 hemodialyzed patients (normocalcemic: n = 14; hypercalcemic: n = 21). The cross-sections of all glands were classified intraoperatively. Diffuse hyperplastic (type 1) and nodular hyperplastic (type 2) glands could be distinguished. Using a stereo-magnifier (magnification: x 10 -x 16), type 1a- (stromal fat cells!) and type 1b- glands (without stromal fat cells!) could be differentiated. Those areas were also found between the nodules of type 2-glands. Significantly, nodular hyperplastic glands predominated in hypercalcemic patients (chi 2-Test: p less than 0.001). The colour of the nodules on the cross-sections of type 2-glands correlated with the predominating cell type ("dark": nodule of oxyphile cells; "medium": nodule of chief cells; "light": nodule of 'degenerating' oxyphile cells). As sign of proliferation the mitotic index was elevated (greater than 1:10,000) in type 1b-glands, in type 1b-like areas and in nodules of type 2-glands. These areas should not be used for autotransplantation.

Parathyroid imaging: its current status and future role

The management of autonomous (primary or tertiary) hyperparathyroidism is controversial for two important reasons: (1) Diagnosis of primary or tertiary hyperparathyroidism (as distinct from reactive or secondary hyperparathyroidism) has been revolutionized in the past 20 years as a result of routine inclusion of serum calcium concentration assays in serum multiautomated analysis, now obtained routinely for both hospitalized as well as ambulatory patients. The prevalence of primary hyperparathyroidism in the general population has appeared to rise as a consequence of this assay and the enhanced detection of this disease. This situation has confused the management of hyperparathyroidism since most patients now present with asymptomatic disease, and the need for surgical treatment is controversial in asymptomatic individuals. (2) Primary hyperparathyroidism usually is caused by hypersecretion of parathyroid hormone by an autonomously functioning parathyroid adenoma. In a small percentage of cases, multigland hyperplasia is present. In experienced hands, surgical removal of an adenoma within the thyroid bed cures the hyperparathyroidism 90% to 95% of the time, without performance of a preoperative procedure to localize the adenoma. Approximately 10% of parathyroid tissue is ectopic in location, however. Furthermore, approximately two thirds of "missed" adenomas are within the thyroid bed. Reexploration in the event of a failed operation therefore is not an uncommon occurrence. Parathyroid localization procedures clearly are indicated in patients with primary hyperparathyroidism who have evidence of persistent disease after a failed attempt at surgical cure. In patients first presenting with primary hyperparathyroidism, the need for a localization procedure is less clear, since surgery appears to be successful much of the time without it. Regardless of the nature of the above controversies, surgery for autonomous hyperparathyroidism continues, and localization procedures become more popular. Preoperative localization procedures such as angiography and venography with venous sampling for parathormone are cumbersome and invasive. Noninvasive tests to localize the parathyroid glands have emerged in the past 10 years, including dual tracer radionuclide scintigraphy with 201-thallous chloride and 99m-technetium pertechnetate, high-resolution computer tomography, and fine parts ultrasonography. Dual tracer scintigraphy with thallium and technetium is reported to have a localization sensitivity of 70%-90%. False-negative studies occur primarily in patients with small adenomatous or hyperplastic glands.(ABSTRACT TRUNCATED AT 400 WORDS)

Parathyroid glands in primary hyperparathyroidism: an ultrastructural study of 50 cases

Parathyroid glands from 50 cases of primary hyperparathyroidism were examined by light and electron microscopy in an attempt to elucidate the diagnostic role of electron microscopy in this disease. In the cases in which only one gland was removed at surgery, a final diagnosis by light microscopy was not possible. The electron microscopic findings for some of these single glands (e.g., ribosomal-lamellar complexes and groups of centrioles) suggested that they were adenomas. In cases in which two or more enlarged glands were removed, a correct final diagnosis could be made on the basis of the light microscopic findings alone, and electron microscopy provided no further significant information. Where one enlarged gland and one normally sized gland were removed, electron microscopy disclosed important findings in the normally sized glands. Specifically, light microscopic examination of normally sized glands suggested endocrine suppression, while electron microscopy showed chief cell activity, thereby changing the final diagnosis from adenoma to hyperplasia. The clinical follow-up assessment in some of these patients confirmed the electron microscopic findings. Therefore, the incidence of adenoma in patients with primary hyperparathyroidism should be critically re-evaluated by ultrastructural studies of the normal glands that should be removed with the enlarged ones.

Pathologic study of parathyroid glands in tertiary hyperparathyroidism

Tertiary hyperparathyroidism is defined as persistent parathyroid hyperfunction developing from the secondary hyperplasia that occurs after restoration of renal function by dialysis or kidney transplantation. Controversy continues as to whether parathyroid adenoma or hyperplasia accounts for the autonomous hyperfunction. A review of 128 parathyroids from 41 patients with tertiary hyperparathyroidism revealed marked hyperplasia in 39 patients (95 per cent), with a predominance of chief cells, an abundance of oxyphil cells, and 10- to 40-fold increases in parathyroid mass. This hyperplasia was considered to be the predominant morphologic feature of tertiary hyperparathyroidism. Adenomas, found only in two patients (5 per cent), seem to be rare. Diffuse, moderately enlarged hyperplastic glands were found predominantly in patients with transplants, whereas nodular, markedly enlarged hyperplastic parathyroids were observed more frequently in patients treated by dialysis. In spite of the different patterns of hyperplasia and the different gland sizes in these two groups of patients, the grades of hypercalcemia were similar. The results of ultrastructural studies indicate that the majority of parenchymal cells in diffuse, and some cellular areas in nodular, hyperplasia may consist of cells with high secretory activity that do not respond normally to hypercalcemia. It is concluded that both increased parenchymal mass and cellular differentiation, leading to hyperactivity, account for tertiary hyperparathyroidism.

Parathyroid pathology in hyperparathyroidism secondary to chronic renal failure

Weights and histopathological changes in parathyroid glands were evaluated in relation to clinical and biochemical parameters in 42 patients who underwent parathyroidectomy for hyperparathyroidism (HPT) secondary to chronic renal failure. There was a positive relation (r = 0.71, p less than 0.01) between duration of renal insufficiency and total parathyroid glandular weight. The glandular weight was also closely related to the serum levels of parathyroid hormone (r = 0.67, p less than 0.01). No correlation was found between total parathyroid glandular weight or histopathological findings and clinical symptoms, serum levels of calcium, phosphate, alkaline phosphatases, calcium X phosphorus product or radiological evidence of bone disease. The enlargement of the glands was mostly uniform in the individual patient and all patients showed multiple gland involvement. This indicates that when parathyroid surgery is performed in patients with uraemia and secondary HPT, a radical approach, i.e. total parathyroidectomy with autotransplantation or subtotal parathyroidectomy, should always be used. In smaller glands only diffuse hyperplasia of parenchymal cells was generally found; fat cells were present in near-normal amounts. With increasing glandular weight, fat cells were more sparse and nodularity was common. In general, the proportion of oxyphil cells increased parallel with the total glandular weight, suggesting that this cell type is sensitive to stimulation. As a group, patients undergoing conservative renal treatment had suffered longer with renal disease, had larger parathyroid glands with more nodularity, and had more oxyphil cells than those undergoing parathyroidectomy while on haemodialysis.

Nuclear diameter in parathyroid disease

The nuclear diameter of chief cells was measured in 17 cases of parathyroid adenomas, four cases of secondary hyperplasia, five cases of primary hyperplasia and six cases of tertiary hyperparathyroidism. All the cases with secondary hyperplasia and tertiary hyperparathyroidism were associated with chronic renal failure. The nuclear diameter in both the adenomatous and hyperplastic areas of tertiary hyperparathyroidism were measured. The adenomatous areas of tertiary hyperparathyroidism contained nuclei of a larger diameter than those in the hyperplastic foci of the same gland. The nuclear diameter in adenomatous foci of tertiary hyperparathyroidism was similar to that in adenomas from primary hyperparathyroidism. These findings lend support to the concept of formation of autonomous adenomas against a background of reactive parathyroid hyperplasia in cases of tertiary hyperparathyroidism. Using statistical methods there were differences between the nuclear diameter in cases of primary adenomata, and cases of primary and secondary hyperplasia. Primary parathyroid hyperplasia stood out as a distinct group. The significance of these findings is discussed.

[Transplantation hyperparathyroidism--tumorlike growth and autonomous function of autografts of the hyperplastic parathyroid (author's transl)]

The results of clinical and morphologic studies performed in 41 patients with chronic, renal failure and secondary hyperparathyroidism, who had total parathyroidectomy and autotransplantation of parathyroid tissue into the forearm muscle are presented. In five cases, 7--33 months after autotransplantation we found transplantation tumors developing in the forearm. Explanted grafts showed invasive growth of parathyroid tissue in the adjacent structures, into the musculature and blood vessels. The increased incidence of mitosis otherwise seen as evidence of malignant neoplasia of parathyroid tumors, indicated atypical focal proliferation of the transplanted tissue. This is justification for not performing transplantations any more in the treatment of renal osteodystrophy.

The normal parathyroid revisited: percentage of stromal fat

The pathologist must frequently decide, on the basis of a small biopsy specimen, whether a parathyroid gland is normal or abnormal. Most references state that the normal parathyroid contains approximately 50 per cent fat and that a reduction in this fat content is characteristic of hyperplasia. The parathyroid glands of 100 consecutively autopsied patients were evaluated, and the observations were correlated with clinical and laboratory findings. In 90 patients with no clinical, laboratory, or pathologic evidence of parathyroid hyperfunction, we found an average parathyroid fat content of 17 per cent ("percentage fat"). Only one patient had more than 50 per cent fat, and almost one third had less than 10 per cen fat. There was no correlation between percentage fat and age, serum calcium level, or gland weight. The findings of four previous quantitative studies were virtually identical with ours. The normal parathyroid gland contains much less fat than is commonly believed, and the range of values in normal persons is large. Determination of stromal fat has limited usefulness in the evaluation of the functional state of the parathyroid gland.

Treatment of secondary hyperparathyroidism in patients with chronic renal failure by total parathyroidectomy and parathyroid autograft

Sixty-one patients with chronic renal failure and secondary hyperparathyroidism underwent total parathyroidectomy and parathyroid autograft. Symptoms relieved by parathyroidectomy included bone pain, pruritus, soft tissue calcification, muscle weakness and healing of fractures. Serum parathormone levels measured before and after operation in 48 patients returned to normal in all but two patients. Serum alkaline phosphatase levels also returned toward normal after operation, except in one patient with a retained parathyroid gland. Complete radiographic studies before and after operation were available in 30 of 61 patients. Twenty-three of 24 patients with osteitis fibrosa had evidence of healing, and in one patient no change occurred. Osteosclerosis noticed in 23 patients improved slightly in eight patients, did not change in 14 and became worse in one. Pathologic examinations revealed 45 patients to have diffuse hyperplasia and 16 nodular hyperplasia. There were two early postoperative deaths, in the first 30 days, and 16 late postoperative deaths, from four months to four years afterward. In no case did the operation contribute to death. Some patients required the administration of supplemental calcium after operation, but in no instance did profound hypocalcemia occur. No patient developed recurrent hyperparathyroidism.

The surgical management of primary hyperparathyroidism: a personal series

Primary hyperparathyroidism includes a spectrum of abnormalities relative to the size and histologic characteristics of the diseased glands. The lack of uniform agreement upon pathological interpretation and discrepancies between gross and histologic findings perpetuate the controversy regarding the mass of parathyroid tissue necessary to be resected. From 1960 to 1978, 193 primary hyperparathyroid patients (aged 20-80 years; mean: 55 years) were operated on by the senior author with a mean follow-up of 41.5 months. An approach evolved that included gross identification of all parathyroid tissue with frozen section confirmation and assessment of cellularity-the latter modifying the extent of parathyroid resection in 11 patients (11%) of 100 patients who had biopsies of at least four parathyroids. Overall persistence and recurrence rates of hypercalcemia were 6.2% (12 patients) and 1% (two patients), respectively, despite routine biopsy in 100 patients. No permanent hypocalcemia developed, but five patients (2.6%) were hypocalcemia one to 16 weeks postoperatively. No operative deaths occurred. Submission of additional parathyroid tissue by routine biopsy disclosed a higher prevalence of nodular hyperplasia than usually found, and the clinical significance of this finding is discussed. With findings based on gross and microscopic intraoperative study, the authors believe, the surgeon is better able to categorize pathologic variants of hyperparathyroidism and better equipped to deal with recurrent disease.

The parathyroid in chronic renal failure-- a light and electron microscopical study

The parathyroids from ten consecutive cases of chronic renal failure coming to operation in a period of seven years were studied by light and electron microscopy. The clinical and biochemical data as well as the levels of immunoreactive parathormone (iPTH) were reviewed. For the sake of comparison adenomata from two cases of primary hyperparathyroidism were studied. In the cases of chronic ;renal failure there were six cases of tertiary hyperparathyroidism with adenoma formation, surrounded by dense fibrous tissue and compression of adjacent parathyroid cell amidst a background of hyperplasia. Two cases showed secondary parathyroid hyperplasia and the remaining two cases were adenomata which clinically affected only one gland. Neither the biochemical data nor levels of iPTH allowed the cases with secondary hyperplasia to be separated from those with tertiary hyperparathyroidism. Similarly electron microscopy showed no distinct differences between these two groups of adenomata from cases of primary hyperparathyroidism. The diagnosis of tertiary hyperparathyroidism is made on a combination of clinical, biochemical and histological features, the histological features being most important. It is concluded that tertiary hyperparathyroidism is part of a histological spectrum in response to chronic renal failure and autonomous glands are related to the mass of parathyroid tissue present.

A functional parathyroid gland adenoma of transitional oxyphil cells. A light and ultrastructural study

This report describes light and ultrastructural features of a functional parathyroid gland adenoma, principally composed of transitional oxyphil cells, in a 64-yr-old hypertensive black woman. She was hospitalized for repeated episodes of headaches, lethargy, and dizzy spells. Her serum calcium level was 2.92 mmol/l and immunoassay for parathormone was 390 pg/ml. On neck exploration, the left lower parathyroid gland was found enlarged and therefore removed in toto. The serum calcium and phosphate levels returned to normal following parathyroidectomy. Microscopically, the diagnosis of functional oxyphil adenoma was made. On ultrastructural examination, the tumour was composed principally of transitional cells, occasional typical, and degenerating oxyphil cells. The predominant transitional cells were rich in mitochondria and contained multiple active Golgi complexes, stacked profiles of rough endoplasmic reticulum, and a few secretory granules. On the other hand, typical oxyphil cells were tightly packed with mitochondria at the expense of other organelles. It appeared that neoplastic oxyphil cells were chief cells transformed in response to some unknown oncogenic stimulus.

The normal parathyroid gland at autopsy: the significance of stromal fat in adult patients

Traditionally half of the cell population of the adult parathyroid gland is considered to be stromal fat. A marked decrease of stromal fat has been observed at autopsy of adult patients, the functional significance of which is unknown. In order to investigate this phenomenon, the stromal and parenchymal fat of the parathyroid glands of 33 adult patients who died with no known hormonal abnormalities were evaluated. Stromal fat was much less than 50 per cent, i.e., less than 10 per cent., in the majority of cases, while parenchymal fat was ample in all cases. This finding, especially if compared to cases with hyperparathyroidism, indicates the lack of functional specificity of change in stromal fat, whereas, alteration in parenchymal fat appears to be a better anatomical register of normal or abnormal parathyroid function.

A histological comparison of adenomatous and hyperplastic parathyroid glands

The histological findings in 18 cases of parathyroid hyperplasia associated with chronic renal failure and haemodialysis have been compared with a series of 35 cases of primary adenomatous hyperparathyroidism. Analysis of several features suggests that there are no definite criteria for distinguishing microscopically between individual enlarged glands in primary and secondary hyperparathyroidism, although nuclear pleomorphism is more common in primary adenoma and nodules are more common in secondary hyperplasia. These findings are discussed.