Nitric Oxide Synthase in Human Parathyroid Glands and Parathyroid Adenomas

Nitric oxide (NO) is a novel gaseous intercellular transmitter thought to play important physiological roles in the regulation of blood flow and hormone secretion in, for example, the pituitary, the thyroid, and the endocrine pancreas. Whether nitric oxide synthase (NOS) is present in the human parathyroid glands has not yet been demonstrated. In the present study, histologically normal, but functionally suppressed human parathyroid glands and parathyroid adenomas from patients with primary hyperparathyroidism were investigated by immunocytochemistry with antibodies against neuronal NOS and by reduced nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase histochemistry. We also used H&E to identify the NOS-immunoreactive cells. Immunocytochemistry demonstrated the presence of neuronal-type NOS in a subpopulation of glandular cells, identified as oxyphilic cells, in both normal parathyroid glands and adenomas. NADPH-diaphorase staining visualized NOS in the endothelium of blood vessels and in glandular cells, corresponding to those containing immunoreactive NOS. In addition, we found NADPIH-diaphorase staining in many chief cells. Our results indicate that both glandular cells and vascular endothelium in human parathyroid glands and adenomas express NOS. There is thus a morphological substrate for locally produced NO that may be involved in the regulation of parathyroid blood flow and hormone secretion.

Peptide-containing nerve fibres in normal human parathyroid glands and in human parathyroid adenomas

There are only a few studies on the innervation of the human parathyroid glands and the content of neurotransmitters. We therefore studied the occurrence and distribution of peptide-containing and adrenergic nerve fibres and the coexistence pattern of neuromessengers by immunocytochemistry in normal (unaffected) and adenomatous parathyroid glands from patients undergoing surgery for parathyroid adenoma. The unaffected parathyroid glands had a moderate-to-rich supply of nerve fibres and terminals containing two general neuronal markers, protein gene product 9.5 (PGP 9.5) and synaptophysin, neuropeptide Y (NPY) and tyrosine hydroxylase (TH). They were seen close to blood vessels and, occasionally, among the endocrine cells. Only a few nerves contained calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP), substance P (SP) and pituitary adenylate cyclase-activating peptide (PACAP). The general density of innervation, using PGP 9.5 and synaptophysin as markers, varied greatly among the different adenomas examined. This applied also to the density of fibres and terminals containing specific types of messengers. Some of the tumours had a rich supply of TH- and NPY-containing nerve fibres, while others contained only few scattered fibres. The CGRP-containing fibres varied from moderate in number to no detectable fibres. The PACAP-, SP- and VIP-containing fibres were always very few or not detectable. It is not inconceivable that the wide variation in general density of the innervation and frequency of peptide-containing nerves among individual parathyroid adenomas is of significance for their hormone secretory behaviour.

Immunoheterogeneity of parathyroid hormone pre- and postoperatively in primary hyperparathyroidism

In primary hyperparathyroidism (pHPT), a preferential release of intact PTH (i-PTH) versus carboxylterminal PTH fragments is known to occur. We studied whether the release of amino-terminal PTH fragments (N-PTH) is also changed. Serum levels of i-PTH and N-PTH were determined under basal conditions and following oral intake of calcium in six patients with pHPT before and immediately after surgery and in seven healthy subjects. In the patients, baseline levels of both i-PTH and N-PTH were increased preoperatively. The increase was larger in i-PTH compared to N-PTH. Therefore, the N/i ratio was reduced compared to healthy subjects (P < 0.05). On the first postoperative day, serum i-PTH decreased to a larger extent than N-PTH, which increased the N/i ratio above that in healthy subjects (P < 0.05). On the 5th postoperative day, the N/i ratio was normalized. Preoperatively, the suppressibility of i-PTH calcium was impaired in the patients (P < 0.05), whereas the suppressibility of N-PTH was normal, resulting in unchanged N/i ratio during the oral calcium load. In contrast, the N/i ratio increased normally during the calcium load at day 5 postoperatively (P < 0.05). We therefore conclude that: (1) in pHPT, circulating PTH immunoheterogeneity is altered with a preferential release of intact PTH compared to N-terminal PTH fragments and this alteration is normalized after surgery, (2) the secretion of intact PTH and N-terminal PTH shows different sensitivity to inhibition by calcium.

Effects of minor increase in serum calcium on the immunoheterogeneity of parathyroid hormone in healthy subjects and in patients with primary hyperparathyroidism

To study possible influences of a mild increase in serum-ionized calcium concentration that is seen during daily life on circulating parathyroid hormone (PTH) immunoheterogeneity, we used sequence-specific PTH assays to determine serum intact PTH, C-terminal PTH and N-terminal PTH following oral calcium (1.5 g) in healthy subjects (n = 7). This was also performed in patients with primary hyperparathyroidism (pHPT; n = 10) to see if their regulation of circulating PTH molecular forms is normal. Compared to healthy subjects, the patients were hypercalcemic (p < 0.05) and had higher levels of PTH in all three assays (p < 0.001). Following the oral calcium load, serum-ionized calcium increased by 0.08 +/- 0.03 mmol/l in the patients and by 0.07 +/- 0.03 mmol/l in the healthy subjects after 90 min, whereas serum intact PTH, C-terminal PTH and N-terminal PTH were reduced, both in the healthy subjects and in the patients. Suppression by calcium of both intact PTH and C-terminal PTH were impaired in the patients (p < 0.05 and p < 0.001), whereas suppression of N-terminal PTH was normal. Furthermore, the C/i and N/i ratios were higher at the highest calcium concentration achieved after calcium intake in the healthy subjects than in the basal state in the patients (p < 0.05), in spite of the larger degree of hypercalcemia in the latter (1.40 +/- 0.06 vs. 1.31 +/- 0.02 mmol/l; p < 0.05). Thus, (1) a minor increase in serum-ionized calcium that is seen during daily life alters the relative circulating concentrations of PTH versus its fragments; (2) the impaired sensitivity to calcium in pHPT is not evident for the suppression of N-terminal PTH, and (3) pHPT is accompanied by altered immunoheterogeneity of circulating PTH.

Immunoheterogeneity of parathyroid hormone after surgery for primary hyperparathyroidism

Circulating parathyroid hormone (PTH) immunoheterogeneity is altered in primary hyperparathyroidism (pHPT). It is not known, however, whether the relative secretion of various PTH fragments differs between the adenomatous and the non-adenomatous glands in pHPT. We therefore examined the immunoheterogeneity of PTH in patients operated upon because of parathyroid adenoma pre- and 4 days postoperatively during an EDTA-infusion test. Following surgery, baseline levels of amino-terminal PTH (N-PTH) were reduced by a smaller degree than the levels of intact PTH (i-PTH) (P < 0.05) resulting in a higher N/i ratio postoperatively (P < 0.05). Furthermore, the increase in i-PTH and C-PTH fragments during the EDTA infusion test was lower postoperatively than preoperatively (P < 0.05), whereas the increase in N-PTH did not differ. The results therefore suggest that compared with the parathyroid adenoma, the non-adenomatous glands secrete relatively more N-terminal PTH.

Functional recovery of the parathyroid glands after surgery for primary hyperparathyroidism

BACKGROUND

The immediate postoperative function of the parathyroid glands after surgery for primary hyperparathyroidism (pHPT) has not been established. We therefore examined the influences of hypercalcemia and hypocalcemia on serum parathyroid hormone (PTH) levels in the immediate postoperative period in patients with pHPT.

METHODS

Ethylenediaminetetraacetic acid was infused in patients on the first (n = 5) and fourth (n = 6) postoperative days, and in patients at 1 year after surgery (n = 6), and in healthy subjects (n = 7). Calcium was given orally before operation and on the second and fifth postoperative days in six patients and in seven healthy subjects.

RESULTS

The increased set point seen in pHPT was normalized on the first postoperative day, and the decreased PTH suppressibility by calcium was normal on the second postoperative day. However, on the fifth postoperative day an increased suppressibility of PTH was evident. During the ethylenediaminetetraacetic acid infusion test the secretory reserve for PTH increased after operation with increasing hypocalcemia-induced levels of intact PTH between the first and fourth postoperative days (p < 0.001), and between the fourth postoperative day and the test at 1 year (p < 0.05).

CONCLUSIONS

In the immediate postoperative period after surgery for pHPT, baseline serum levels of PTH are rapidly normalized; this is followed by an increase in the secretory reserve for PTH secretion and the development of an increased sensitivity to calcium.

Hyperthyroxinemia after surgery for primary hyperparathyroidism

Episodes of transient thyrotoxicosis after surgery for primary hyperparathyroidism have previously been described, and surgical trauma to the thyroid gland has been suggested as an etiologic factor. However, there are several links between the thyroid and parathyroid hormonal systems, and therefore other explanations are possible as well. In this study we investigate pre- and postoperative serum levels of thyroid hormones in 20 patients operated upon because of primary hyperparathyroidism. The mean (SD) serum levels of T4 increased from 16(2) pmol/l preoperatively to 21(6) pmol/l on the fourth postoperative day (P < 0.01), and four (20%) of the patients developed biochemical thyrotoxicosis in the immediate postoperative period. The serum levels of T4 on the fourth postoperative day correlated highly with preoperative serum levels of PTH (r = 0.75; P < 0.001). This suggests that biochemical thyrotoxicosis in the immediate postoperative period after operation for primary hyperparathyroidism is not uncommon and could be related to the disease rather than to surgical trauma.

Serum levels of thyrotropin are decreased by oral calcium in healthy subjects but not in patients with primary hyperparathyroidism

It has been suggested that calcium changes the set point of the pituitary thyroid feedback. It is not known, however, if small and slow changes of calcium and/or parathyroid hormone (PTH) within the physiological range influence the serum levels of thyrotropin (TSH) and thyroid hormones in healthy subjects or patients with primary hyperparathyroidism (pHPT). Nine healthy subjects and nine patients with pHPT were therefore investigated with an oral calcium load test. The patients were investigated before and 4 days after operation. During the test, serum levels of ionized calcium increased and serum levels of intact PTH decreased in both healthy subjects and patients pre- and postoperatively (p < 0.001). Furthermore, in patients, the suppressibility of serum levels of PTH by calcium increased postoperatively (p < 0.05). Serum levels of TSH decreased during the oral calcium load in healthy subjects (p < 0.01) but not in patients, whereas the serum levels of thyroid hormones did not change. It is concluded that oral calcium influences TSH secretion in healthy humans but not in patients with pHPT.

Intraoperative monitoring of intact PTH during surgery for primary hyperparathyroidism

The intraoperative differential diagnosis between adenoma and hyperplasia during surgery for primary hyperparathyroidism (pHPT) is sometimes difficult. Several methods have been proposed to aid the surgeon in deciding on the amount of parathyroid tissue to be resected. We examined the use of intraoperative monitoring of intact PTH in 47 patients operated upon for pHPT. The highly sensitive assay for intact PTH was modified to permit a total turn-around time from gland excision to obtained result of about 60 min. The correlation (r) between the results of the modified and the conventional method, which requires 24 h of incubation, was 0.98. At 15 min after removal of the parathyroid adenoma the levels of intact PTH had decreased by [mean (SD)] 85 (11)%. A decrease of 63% in intact PTH in patients with parathyroid adenoma predicted with 95% confidence the 4 patients with primary hyperplasia as not having parathyroid adenoma. We conclude that intraoperative measurement of intact PTH could be a valuable adjunct to surgical skill, especially for reoperative parathyroid surgery.

Suppressibility of serum levels of PTH by calcium in the immediate postoperative period after surgery for primary hyperparathyroidism

The ability of calcium to suppress the secretion of parathyroid hormone (PTH) is impaired in primary hyperparathyroidism (pHPT). Whether the nonadenomatous glands in pHPT also exhibit altered calcium/PTH homeostasis is not known, but this may be the case since in the immediate postoperative period after surgery for pHPT, hypocalcemia often evolves in spite of a rapid normalization of serum levels of PTH. In this study, therefore, the suppression of serum levels of PTH by an oral calcium load was investigated pre- and postoperatively in 12 patients operated on for parathyroid adenoma. There was no difference in the calcemic response during the calcium load pre- and postoperatively. We found that the suppression of serum levels of PTH by calcium was increased already on the first postoperative day. However, postoperatively, the suppression of serum levels of PTH correlated positively to serum levels of ionized calcium and, furthermore, negatively to the weight of the excised parathyroid adenoma and the preoperative serum levels of ionized calcium. The results indicate that the function of the remaining parathyroid glands in patients with parathyroid adenoma could have been altered during the hyperparathyroid state and that postoperative hypocalcemia more readily evolves in patients with severe pHPT and impaired suppressibility of PTH (by calcium) in the remaining parathyroid glands.

Postoperative studies on parathyroid hormone secretion in patients operated on for primary hyperparathyroidism

The secretion of intact parathyroid hormone (PTH) was investigated in 11 patients operated on for parathyroid adenoma at 1 year after surgery and compared with that of seven healthy individuals and five patients operated on because of clinical and biochemical signs of primary hyperparathyroidism with equivocal diagnosis after surgery. The investigation was performed by infusing Na2EDTA and CaCl2 at constant rates. No significant difference was found in the suppressibility of PTH secretion by calcium. The set point (the calcium concentration required for half-maximal inhibition of PTH secretion) was slightly lower in patients (1.20 +/- 0.02 mmol/l) compared with healthy subjects (1.23 +/- 0.03 mmol/l; P < 0.05). During the hypocalcemic EDTA infusion, the secretion of PTH was higher in controls compared with patients (P < 0.01). By comparing the data from the infusion tests in patients operated on for parathyroid adenomas with the data obtained from the patients with equivocal diagnosis after parathyroid surgery, a good probability for the diagnosis could be obtained.

Potential clinical use of the EDTA-infusion test

The introduction of assays for the intact parathyrin (parathyroid hormone) has dramatically improved the diagnosis and follow-up of patients with primary hyperparathyroidism. However, in some patients with mild or intermittent hypercalcaemia, when plasma concentrations of intact parathyrin may be within the normal reference concentrations, the diagnosis of primary hyperparathyroidism may still be problematic. In these patients, the EDTA-infusion test is of potential value, as it also might be in patients with equivocal operative findings.

Parathyroid hormone secretion after operation for primary hyperparathyroidism

BACKGROUND

Primary hyperparathyroidism (pHPT) is associated with a defective regulation of the secretion of parathyroid hormone (PTH). Thus in pHPT, higher than normal calcium concentrations are required to inhibit PTH release. However, it is not known if this defective regulation is normalized by removal of the parathyroid adenoma (i.e., whether the regulation of PTH secretion is normal in the remaining glands). In this study we therefore investigated the PTH secretion in patients operated on for parathyroid adenoma 1 year after operation.

METHODS

Na2 ethylenediamine tetraacetic acid and CaCI2 were infused at constant rates in six patients operated on for parathyroid adenoma and six healthy individuals. Serum levels of intact PTH and ionized calcium were determined during the infusions.

RESULTS

No significant differences between the two groups were found in baseline levels of serum ionized calcium and PTH. Furthermore, no significant differences between patients and control subjects were found in the maximum serum PTH levels during the hypocalcemic infusion of ethylenediamine tetraacetic acid or in the minimum serum PTH levels during the calcium infusion. In contrast, the set point (the calcium concentration required for half-maximal inhibition of PTH secretion) was significantly lower in the patients (1.20 +/- 0.01 mmol/L) compared with control subjects (1.22 +/- 0.01 mmol/L; p < 0.05).

CONCLUSIONS

We conclude that the elevation of set point in patients with parathyroid adenoma is corrected by successful operation. This suggests a monoclonal origin of parathyroid adenomas.

Suppression by calcium of serum levels of intact parathyroid hormone in patients with primary hyperparathyroidism

Primary hyperparathyroidism (pHPT) is associated with a right-shifted relation between parathyroid hormone (PTH) secretion and calcium. However, it is also possible that a decreased suppressibility of PTH secretion by calcium is important for maintaining hypercalcemia in pHPT. We therefore compared the suppression of serum levels of intact PTH induced by a 1.5-gram oral calcium load in patients with mild pHPT with that in healthy subjects. The calcemic response to the oral calcium load was the same in the two groups and did not correlate with the degree of PTH suppression or to serum levels of vitamin D metabolites. It was found that serum levels of intact PTH were less suppressed by the oral calcium load in patients than in healthy subjects (p < 0.01), but with a considerable overlap between the two groups. The suppression of serum levels of intact PTH was correlated both to baseline serum total calcium levels (r = -0.55; p < 0.05) and osteocalcin levels (r = -0.69; p < 0.05) in the patients, but no such correlations were seen in the controls. We conclude that patients with pHPT have a decreased suppressibility of PTH secretion by calcium. Although this reduced suppressibility could be important for maintaining hypercalcemia in some patients with pHPT, it does not aid in the differential diagnosis between patients with mild pHPT and healthy subjects.

Calcium metabolism after hemithyroidectomy

It is not known whether thyroid surgery evokes changes in calcium metabolism. We therefore studied 6 patients operated upon with hemithyroidectomy for benign thyroid diseases, preoperatively and at 3 months and 1 year postoperatively. We measured changes in serum levels of intact parathyroid hormone (PTH), vitamin D metabolites, ionized calcium, phosphate, osteocalcin, thyroid hormones and bone density. Further, the dynamic function of the parathyroid glands was investigated by an oral calcium load test pre- and at 3 months postoperatively. At follow-up, all patients were euthyroid. During the oral calcium load, serum levels of intact PTH were reduced by the same degree before and after hemithyroidectomy, showing normal parathyroid function. Serum levels of 1,25-dihydroxyvitamin D declined from 86 +/- 16 to 57 +/- 4 pmol/l (p < 0.01) at 1 year after hemithyroidectomy, and serum levels of phosphate increased slightly from 0.96 +/- 0.08 to 1.06 +/- 0.08 mmol/l (p < 0.05), whereas serum levels of ionized calcium, intact PTH, osteocalcin and bone density did not change. Our results demonstrate that thyroid operation evokes changes in vitamin D metabolism in spite of normal parathyroid function.

Large vein sampling for intact parathyroid hormone in preoperative localization of enlarged parathyroid glands

Unilateral neck exploration for primary hyperparathyroidism (pHPT) of old and high risk patients can be safely performed under local anesthesia, provided there is a correct preoperative side localization of the enlarged parathyroid gland. We performed large vein sampling and measured intact parathyroid hormones (PTH) with a new, highly sensitive immunoradiometric assay. The method was used before operation in 20 patients with pHPT. A unilateral positive gradient of serum PTH levels was obtained in 15 patients. At surgery, 13 of these (87%) proved to be correct, i.e., the adenoma was localized on the same side. Thus, the technique correctly lateralized the parathyroid adenoma in 65% of the patients. We conclude that large vein sampling with measurement of intact PTH is a potentially useful investigation for preoperative side localization of parathyroid adenomas in pHPT patients scheduled for unilateral surgery under local anesthesia. However, prior to routine bilateral neck exploration large vein sampling is not justified.

Surgery for primary hyperparathyroidism performed under local anaesthesia

Patients with primary hyperparathyroidism are often elderly with cardiovascular disease and in some an operation might be hazardous owing to anaesthetic complications. A technique for operation for primary hyperparathyroidism under local anaesthesia is described. The method uses a unilateral approach. Seventeen consecutive patients operated on under local anaesthesia were compared with a group of 15 patients undergoing surgery under general anaesthesia. Normocalcaemia was achieved in 14 patients in each group. There was no difference in the extent of pain or the overall well-being between the two groups as determined by a visual analogue scale. Patients receiving local anaesthesia, however, experienced significantly less nausea after operation (P < 0.01). There was more fluctuation in blood pressure and heart rate in the general anaesthesia group compared with the other group. Surgery for primary hyperparathyroidism can be performed safely under local anaesthesia, and could be offered to patients if general anaesthesia were not suitable or involved an increased perioperative risk. It should not be recommended for routine use in patients who are fit for general anaesthesia.

Thallium-technetium subtraction scintigraphy of enlarged parathyroid glands after calcitonin stimulation of parathyroid hormone secretion

To improve the sensitivity of thallium-technetium subtraction scintigraphy for preoperative localization procedure of enlarged parathyroid glands in primary hyperparathyroidism, we administered calcitonin intramuscularly 4 hours before the scintigraphy in 14 consecutive patients. Injection of calcitonin reduced plasma levels of ionized calcium from 1.47 +/- 0.10 mmol/l to 1.41 +/- 0.09 mmol/l (p less than 0.01). Concomitantly, serum levels of intact parathyroid hormone increased from 6.4 +/- 2.5 pmol/l to 7.9 +/- 2.6 pmol/l (p less than 0.001). The scintigram after calcitonin injection visualized 11 adenomas (sensitivity 78%) compared to only 9 (sensitivity 64%) in conventional scintigrams. In addition, 5 of the adenomas were more distinctly imaged in the scintigram after calcitonin injection, whereas in only one patient was the conventional scintigram better. Thus, the calcitonin injection improved the scintigram in 7 cases and was inferior in only one case (p = 0.031). We conclude that stimulation of parathyroid hormone secretion with calcitonin results in a better preoperative localization of enlarged parathyroid glands in primary hyperparathyroidism.

Serum osteocalcin levels do not change during rapidly induced hypercalcemia in healthy subjects

Since osteocalcin has been suggested to play a role in calcium homeostasis, we investigated its serum levels in 6 healthy subjects during a rapid calcium infusion. Serum levels of intact parathyroid hormone (PTH), 25-hydroxyvitamin D [25-(OH) D3] and 1,25-dihydroxyvitamin D [1,25-(OH)2 D3] were also determined. The calcium infusion increased plasma-ionized calcium levels from 1.25 +/- 0.04 to 1.54 +/- 0.07 mmol/l at 30 min (p less than 0.05). Concomitantly, serum levels of intact PTH declined from 2.1 +/- 0.9 to 0.2 +/- 0.3 mmol/l (p less than 0.05). In contrast, serum osteocalcin levels did not change. Further, during calcium infusion, serum levels of 1,25-(OH)2 D3 decreased from 81 +/- 17 to 75 +/- 15 pmol/l (p less than 0.05) whereas serum levels of 25-(OH) D3 did not change. The results therefore suggest that calcium per se does not influence osteocalcin secretion.

Measurement of intact parathyroid hormone in the diagnosis of hyperparathyroidism

Plasma levels of parathyroid hormone were determined pre-operatively in 27 consecutive patients with clinical and biochemical signs of primary hyperparathyroidism, by the use of one assay recognizing the intact PTH molecule and one assay recognizing the mid-portion of PTH. Plasma levels of mid-molecule PTH were normal in 5 of the patients with primary hyperparathyroidism. In 4 of these patients, plasma levels of intact PTH were raised. Conversely, in 6 patients with primary hyperparathyroidism, intact PTH were normal pre-operatively. In 5 of these cases, plasma levels of mid-molecule PTH were raised. The EDTA infusion test was performed in 6 patients with normal baseline plasma level of intact PTH pre-operatively. The test correctly predicted all the patients in this group who were found to have primary hyperparathyroidism, as well as a patient with normal parathyroid glands found at operation. We conclude that some patients with primary hyperparathyroidism have normal baseline plasma levels of intact PTH. In these patients, plasma levels of mid-molecule PTH and an EDTA infusion test provide further diagnostic information.

Preoperative localization of enlarged parathyroid glands with ultrasonically guided fine needle aspiration for parathyroid hormone assay

For preoperative localization of enlarged parathyroid glands, several imaging techniques have been used. In this study we demonstrate the feasibility of using ultrasonography with fine needle aspiration for parathyroid hormone assay as a preoperative localization procedure in 21 patients with primary hyperparathyroidism. A single adenoma was found in 18 patients while 3 patients had multiglandular disease. Ultrasonically guided fine needle biopsy was possible in 11 cases. In 8 of these aspirates, a high parathyroid hormone content was found. In all 8 cases the localization was confirmed at surgery. We conclude that the efficiency to preoperatively localize enlarged parathyroid glands is enhanced by fine needle aspiration.

Intact parathyroid hormone assay is superior to mid region assay in the EDTA-infusion test in hyperparathyroidism

We examined the use of an intact parathyroid hormone two-site immunoradiometric assay compared with a mid region parathyroid hormone radioimmunoassay in ethylene diamine tetraacetic acid-infusion test in 15 patients with hyperparathyroidism. During the test, plasma intact parathyroid hormone levels increased by 240 +/- 43%, whereas the plasma levels of mid molecule parathyroid hormone increased by only 65 +/- 17%, which is significantly lower (P less than 0.01). Four patients had no increase in plasma mid molecule parathyroid hormone level but still a large increase in plasma intact parathyroid hormone level (P less than 0.01). Thus, plasma measurement of intact parathyroid hormone is superior to that of mid molecule parathyroid hormone in the ethylene diamine tetraacetic acid-infusion test in patients with hyperparathyroidism.

Intraoperative fall in plasma levels of intact parathyroid hormone after removal of one enlarged parathyroid gland in hyperparathyroid patients

Plasma levels of intact parathyroid hormone (PTH) were measured intraoperatively before and after removal of one enlarged gland in 20 hyperparathyroid patients. In 13 patients with a single parathyroid adenoma, plasma levels of intact PTH-(1-84) had declined at 15 min after removal of the adenoma by 86.5 +/- 4.4% of baseline in the antecubital vein and by 85.6 +/- 4.2% in the ipsilateral internal jugular vein. In seven patients with parathyroid hyperplasia, the corresponding figures for decline at 15 min after removal of one enlarged parathyroid gland were only 26.6 +/- 6.4% and 7.8 +/- 29.4%. The fall in PTH levels was significantly less in hyperplasia than in adenoma (p less than 0.001). Thus 15 min after removal of one enlarged parathyroid gland, the decline in plasma level of intact PTH may distinguish between single adenoma and multiglandular disease as the cause of hyperparathyroidism.