Parathyroid function and bone metabolic markers in primary and secondary hyperparathyroidism

Biochemical bone turnover markers in hormonal disorders in adults: a narrative review

BACKGROUND

Hormonal disorders are often associated with abnormal levels of bone turnover markers (BTMs). N-terminal propeptide of type I procollagen (PINP) and serum C-terminal cross-linking telopeptide of type I collagen (CTX-I) are the reference markers of bone formation and bone resorption, respectively.

METHODS

A comprehensive literature search within the MEDLINE and Web of Science databases was performed.

RESULTS

Acromegaly is associated with higher BTM levels, which decrease during the remission after treatment. Adult-onset growth hormone deficiency is often associated with decreased BTM levels. Growth hormone replacement therapy stimulates bone turnover and increases BTM levels. Hypothyroidism is characterized by general slowing of bone metabolism which is reflected by lower BTM levels. The replacement thyroid hormone therapy increases the bone turnover rate and BTM levels increase. Patients with thyroid cancer receive a suppressive dose of thyroid hormones and may have slightly elevated BTM levels. Patients with overt hyperthyroidism had higher BTM levels and anti-thyroid therapy induces a rapid decrease in the BTM levels. Patients with overt primary hyperparathyroidism have higher BTM levels, whereas those with asymptomatic and normocalcemic hyperparathyroidism usually have normal BTM levels. Hypoparathyroidism is characterized by slightly decreased BTM levels. Cushing's syndrome is characterized consistently by markedly decreased osteocalcin concentration, whereas data on other BTMs are discordant.

CONCLUSIONS

BTMs help us to better understand mechanisms of the impact of hormonal disorders and their treatment on bone metabolism. However, it is unknown whether BTMs may be used to monitor the effect of their treatments on bone in the clinical practice.

The usefulness of high pre-operative levels of serum type I collagen bone markers for the prediction of changes in bone mineral density after parathyroidectomy

BACKGROUND

Amino-terminal procollagen propeptide of type I collagen (P1NP) and cross-linked C-terminal telopeptide of type I collagen (βCTX) are two of the more sensitive bone markers for reflecting and monitoring patients with an increased bone turnover as observed in primary hyperparathyroidism (PHPT) patients.

AIM

The present study was performed to evaluate the trend of type I collagen markers one year after parathyroidectomy (PTX) and to examine the relationships between serum P1NP and βCTX levels and bone mineral density (BMD) change after PTX in PHPT Spanish patients.

MATERIALS AND METHODS

Fifty-three PHPT patients were enroled and were followed for one year by measuring lumbar BMD, lumbar t-score, lumbar z-score, PTH, calcium, phosphorus, P1NP and βCTX.

RESULTS

Pre-surgery concentrations of both markers were elevated (P1NP: 90.71±5.03; βCTX: 1.52±0.44). A significant decrease was observed in mean post-operative βCTX and P1NP concentrations (p<0.0001). Levels of BMD, t-score and z-score at lumbar spine were relatively low (BMD: 0.75±0.16; z-score -0.90±0.23; t-score -2.51±0.32); after PTX a significant increase was observed in the levels of these three parameters. P1NP and βCTX were correlated with lumbar BMD change one year after PTX (P1NP: r=0.79, p=0.016; βCTX: r=0.89, p=0.003).

CONCLUSIONS

Pre-surgery concentrations of both bone markers were elevated and a significant decrease after PTX was found. Serum βCTX and P1NP levels were potently related to lumbar BMD changes over one year after PTX. The measurement of βCTX and P1NP would be useful to predict long-term changes in lumbar BMD after PTX.

Cinacalcet reduces serum calcium concentrations in patients with intractable primary hyperparathyroidism

CONTEXT

Patients with persistent primary hyperparathyroidism (PHPT) after parathyroidectomy or with contraindications to parathyroidectomy often require chronic treatment for hypercalcemia.

OBJECTIVE

The objective of the study was to assess the ability of the calcimimetic, cinacalcet, to reduce serum calcium in patients with intractable PHPT.

DESIGN

This was an open-label, single-arm study comprising a titration phase of variable duration (2-16 wk) and a maintenance phase of up to 136 wk.

SETTING

The study was conducted at 23 centers in Europe, the United States, and Canada.

PATIENTS

The study included 17 patients with intractable PHPT and serum calcium greater than 12.5 mg/dl (3.1 mmol/liter).

INTERVENTION

During the titration phase, cinacalcet dosages were titrated every 2 wk (30 mg twice daily to 90 mg four times daily) for 16 wk until serum calcium was 10 mg/dl or less (2.5 mmol/liter). If serum calcium increased during the maintenance phase, additional increases in the cinacalcet dose were permitted.

MAIN OUTCOME MEASURE

The primary end point was the proportion of patients experiencing a reduction in serum calcium of 1 mg/dl or greater (0.25 mmol/liter) at the end of the titration phase.

RESULTS

Mean +/- sd baseline serum calcium was 12.7 +/- 0.8 mg/dl (3.2 +/- 0.2 mmol/liter). At the end of titration, a 1 mg/dl or greater reduction in serum calcium was achieved in 15 patients (88%). Fifteen patients (88%) experienced treatment-related adverse events, none of which were serious. The most common adverse events were nausea, vomiting, and paresthesias.

CONCLUSIONS

In patients with intractable PHPT, cinacalcet reduces serum calcium, is generally well tolerated, and has the potential to fulfill an unmet medical need.

Surgical treatment of secondary hyperparathyroidism due to chronic kidney disease

It is a great honour for me to have this opportunity to present a review about surgical treatment of secondary hyperparathyroidism (2HPT) due to chronic kidney disease (CKD). Uppsala is a historical place concerning the parathyroid gland, because it was here that Ivar Sandström in 1877 initially discovered the small organs, Glandulae Parathyroideae, existing around the thyroid gland in human beings. This finding led to intensive studies of the parathyroid glands, focusing on their histopathology, pathophysiology, clinical diagnosis, and medical and surgical treatment (1) and investigations are still continuing in Uppsala today. I had the privilege to stay in Uppsala during 1989 to study the surgery and pathology of parathyroid glands and it was a pleasure to share clinical and basic research about these small and charming organs with my colleagues in Uppsala.

Stimulation of interleukin-6 promoter by parathyroid hormone, tumor necrosis factor alpha, and interleukin-1beta in UMR-106 osteoblastic cells is inhibited by protein kinase C antagonists

To investigate the level at which protein kinase C (PKC) regulates expression of interleukin-6 (IL-6) in osteoblastic cells, effects of several PKC antagonists and PKC down-regulation by phorbol ester were studied in UMR-106 osteoblastic cells that had been transiently transfected with a -224/+11-base pair (bp) IL-6 promoter coupled to a luciferase reporter. Parathyroid hormone (PTH) elicited a dose-dependent stimulation of the IL-6 promoter expression, with significant increases produced by 5 h of treatment with concentrations of PTH as low as 10(-14) M. The increase in IL-6 promoter expression was inhibited by the PKC antagonists GF109203X, 30 nM to 1 microM, and calphostin C, 250 nM. Prior down-regulation of PKC with 100 nM phorbol-12,13-dibutyrate (PDBU) for 48 h inhibited the PTH effect as well as the smaller stimulatory effects elicited by tumor necrosis factor alpha (TNF-alpha), 10(-9)-10(-8) M, and by IL-1beta, 1-10 ng/ml. In contrast to these findings, the stimulatory effects of PTH, TNF-alpha, and IL-1beta on the IL-6 promoter expression were enhanced by staurosporine. Treatment with GF109203X or down-regulation of PKC with PDBU prevented the stimulatory effects of staurosporine. PKC activity was increased by staurosporine. The findings with staurosporine are consistent with our earlier observations that this agent enhances the calcium signaling and bone resorption elicited by PTH. The studies support the role of PKC in the stimulatory effects of PTH, TNF-alpha, and IL-1beta on IL-6 expression.

Natural history of primary hyperparathyroidism

Primary hyperparathyroidism has evolved into a disorder that is largely asymptomatic. Nevertheless, there is ample evidence of target organ effects even in asymptomatic patients. Recent data suggest that the disease is stable in most asymptomatic patients. Little change is observed in biochemical parameters or bone mineral density over time. A subgroup of asymptomatic patients shows biochemical evidence of disease progression, although, in the author's series, no overt clinical complications developed. Surgical cure is associated with biochemical normalization and increased bone density. Several important questions remain: What are the neuropsychiatric and cardiovascular features of the disease? Are these features progressive over time, and do they regress with cure? What implications do any cardiovascular manifestations have on mortality? Is there an increase in fractures associated with mild asymptomatic disease? Is there an increase in fractures at more cortical sites, with a decrease in vertebral fractures in affected postmenopausal women? Although ongoing targeted research should answer some of these questions, a large multicenter trial is necessary to provide the data needed concerning the natural history of primary hyperparathyroidism.

Serial changes in bone mineral density and bone turnover after correction of secondary hyperparathyroidism in a patient with pseudohypoparathyroidism type Ib

Pseudohypoparathyroidism (PHP) is a disorder characterized by hypocalcemia and secondary hyperparathyroidism caused by primarily renal resistance to the effects of parathyroid hormone (PTH). However, as an indication of normal PTH responsiveness in bone, some patients with PHP develop skeletal disease because of longstanding secondary hyperparathyroidism. A patient is described with hypocalcemia, hyperphosphatemia, marked secondary hyperparathyroidism, and an increased alkaline phosphatase level. Subsequent evaluation revealed a diagnosis of PHP type Ib. The patient had radiographic evidence of skeletal disease caused by secondary hyperparathyroidism. A urinary level of N-telopeptide cross-links of type I collagen (NTX) was elevated markedly. Bone mineral density (BMD) was in the normal range at all measured sites, with BMD at the spine being higher than at the femur and distal radius. Treatment was initiated with calcium and calcitriol. Seven months later, calcium and PTH levels had normalized. The level of urinary NTX fell by 83%. Spinal BMD improved by 15%, and BMD at the femoral neck improved by 11%. Radial BMD was unchanged. This case emphasizes the importance of evaluating patients with PHP for hyperparathyroid bone disease and shows that correction of secondary hyperparathyroidism in patients with PHP can result in a significant suppression of previously accelerated bone turnover and to substantial gains in BMD at sites containing a major percentage of cancellous bone. The case also implies that assessment of bone turnover with urinary NTX and measurement of BMD with dual-energy X-ray absorptiometry (DEXA) may be useful in following the response of the skeleton to therapy in these patients and suggests the need for more studies of both NTX and BMD in patients with PHP.

Bone metabolic analysis in patients with primary hyperparathyroidism

Surgical treatment for primary hyperparathyroidism (PHPT) improves not only the calcium and phosphate metabolism but also the bone metabolism. This study was conducted to analyze the bone metabolism after PHPT operations. Bone mineral density (BMD) was measured by dual-photon absorptiometry in 50 patients before and after operation. Osteocalcin (OC) and alkaline-phosphatase activity (Alp) in serum were measured before and after surgery as markers of bone formation, and urinary deoxypiridinorine (DPD) as an index of osteoclast activity. The 50 patients under study were 40 women (80%) and ten men (20%). Increases in BMD at the lumbar spine were remarkable at three months following operation. Slow but steady progress was made until six months, reaching a plateau thereafter. The increase in BMD of lumbar spine was approximately 10%. Urinary DPD was the most sensitive among the three bone metabolic markers. Although serum Alp and OC remained high after operation, urinary DPD was normalized earlier. The discrepancy of bone formation and resorption was shown after operation and this contributed to the increases in BMD in the first six months.

Primary hyperparathyroidism: short-term changes in bone remodeling and bone mineral density following parathyroidectomy

Changes in bone remodeling and bone mineral density were observed during a period of 6 months after surgery in 24 patients with primary hyperparathyroidism (20 women and 4 men; age 54+/-12 years, range 26-69 years). All bone markers declined significantly within the 6 month follow-up period, but the time course for changes in renal N-terminal telopeptide of type 1 collagen (NTx) excretion differed from those of the other markers by a steep and significant reduction (p < 0.05) after less than 1 month. During the 6 month period, bone mineral density (BMD) increased significantly at all sites measured (p < 0.05) apart from the femoral neck and the proximal and midforearm. The greatest increase of 4.2% was observed in the trochanteric region (p < 0.001). The increase in BMD in spine, trochanteric, and intertrochanteric regions of the hip correlated inversely with baseline forearm BMD values (p < 0.05). Baseline bone markers (serum alkaline phosphatase [AP], serum bone AP, serum pyridinoline crosslinked telopeptide of type 1 collagen, urinary hydroxyproline, urinary osteocalcin), as well as baseline histomorphometric indices of bone turnover (eroded and labeled surface, bone formation rate, activation frequency, and cortical porosity) were positively correlated with changes in spinal BMD over 6 months (p < 0.05). It was concluded that, within 6 months after parathyroidectomy, patients with primary hyperparathyroidism obtain normalization of bone remodeling and a substantial increase in bone mineral density in regions rich in cancellous bone but no significant changes in regions with predominantly cortical bone.