Estrogen replacement may be an alternative to parathyroid surgery for the treatment of osteoporosis in elderly postmenopausal women presenting with primary hyperparathyroidism: a preliminary report

Protein array test detected three osteoporosis related plasma inflammatory cytokines in Chinese postmenopausal women

Inflammatory cytokines were involved in pathological conditions of osteoporosis (OP). However, the specific OP-associated inflammatory cytokines are still awaiting to be detected by using a systemic method. Herein, we adopted an extreme sampling scheme and examined inflammatory cytokines between subjects with low and high bone mineral density (BMD) through protein microarray. First, 8 candidate cytokines including B lymphocyte chemoattractant (BLC), osteopontin (OPN) and insulin-like growth factor-binding protein 4 (IGFBP4) were identified in the discovery extreme sampling subgroup. Then, the different expressions for BLC, OPN and IGFBP4 were validated and replicated in two independent extreme sampling subgroups. Further functional experiments showed that the cytokine BLC was involved in bone metabolism by inhibiting bone formation and promoting bone resorption. Together, this study further revealed that inflammatory cytokines were closely related with OP, and that they highlighted critical roles of BLC in the pathogenesis of OP.

Bone turnover markers in primary hyperparathyroidism

Primary hyperparathyroidism is an endocrine disorder characterized by elevated or inappropriate normal levels of parathyroid hormone in a setting of hypercalcemia. The inclusion of calcium on the basic metabolic bone panel has allowed this disorder to be diagnosed even in the absence of symptoms. Nevertheless, the skeleton can be a target of excess parathyroid hormone activity even during its asymptomatic presentation. Bone turnover markers a surrogate index of the process of the remodeling process at the level of bone, and thus can be useful to monitor skeleton involvement in primary hyperparathyroidism.

Evidence of a functional estrogen receptor in parathyroid adenomas

CONTEXT

Primary hyperparathyroidism (PHPT) is most frequently present in postmenopausal women. Although the involvement of estrogen has been suggested, current literature indicates that parathyroid tumors are estrogen receptor (ER) α negative.

OBJECTIVE

The aim of the study was to evaluate the expression of ERs and their putative function in parathyroid tumors.

DESIGN

A panel of 37 parathyroid tumors was analyzed for expression and promoter methylation of the ESR1 and ESR2 genes as well as expression of the ERα and ERβ1/ERβ2 proteins. Transcriptome changes in primary cultures of parathyroid adenoma cells after treatment with the selective ERβ1 agonist diarylpropionitrile (DPN) and 4-hydroxytamoxifen were identified using next-generation RNA sequencing.

RESULTS

Immunohistochemistry revealed very low expression of ERα, whereas all informative tumors expressed ERβ1 (n = 35) and ERβ2 (n = 34). Decreased nuclear staining intensity and mosaic pattern of positive and negative nuclei of ERβ1 were significantly associated with larger tumor size. Tumor ESR2 levels were significantly higher in female vs. male cases. In cultured cells, significantly increased numbers of genes with modified expression were detected after 48 h, compared to 24-h treatments with DPN or 4-hydroxytamoxifen, including the parathyroid-related genes CASR, VDR, JUN, CALR, and ORAI2. Bioinformatic analysis of transcriptome changes after DPN treatment revealed significant enrichment in gene sets coupled to ER activation, and a highly significant similarity to tumor cells undergoing apoptosis.

CONCLUSIONS

Parathyroid tumors express ERβ1 and ERβ2. Transcriptional changes after ERβ1 activation and correlation to clinical features point to a role of estrogen signaling in parathyroid function and disease.

Cinacalcet for the treatment of primary hyperparathyroidism

The objective of this article is to review the literature regarding the treatment of primary hyperparathyroidism (PHPT) with a focus on cinacalcet. A MEDLINE (1965-June 2009) and bibliographic search of the English-language literature was conducted using the search terms cinacalcet, calcimimetics, primary hyperparathyroidism, and treatment. All articles identified in the search were included. Parathyroidectomy is curative for patients with PHPT; however, there are few options for patients who are not surgical candidates, who refuse surgery, or those with refractory PHPT after parathyroidectomy. Possible treatment options include estrogens, raloxifene, bisphosphonates, calcitonin, and cinacalcet. Cinacalcet has been shown to decrease serum calcium and parathyroid hormone serum levels in patients with PHPT. These trials, however, have not studied the effect of cinacalcet on patient-oriented outcomes such as bone mineral density, nephrolithiasis, or other complications of PHPT. Cinacalcet may be considered to reduce serum calcium and parathyroid hormone serum levels in patients with PHPT who cannot or will not undergo surgery and those with refractory PHPT after parathyroidectomy. Because the effects of cinacalcet on bone mineral density are uncertain, more frequent monitoring of bone mineral density may be required along with a medication proven to improve bone mineral density. Future studies should evaluate the effect of cinacalcet on complications of PHPT.

Should 'mild primary hyperparathyroidism' be reclassified as 'insidious': is it time to reconsider?

Primary hyperparathyroidism (PHPT) is a common incidental finding on routine biochemical testing, affecting around 1% of the population. The majority of individuals will be asymptomatic at diagnosis, with no evidence of end organ damage, and unless individuals aged <50 years at diagnosis, they are often considered to have 'mild' PHPT, as they do not meet published criteria for parathyroidectomy (PTX). However, there is increasing evidence that 'mild' PHPT is associated with adverse health outcomes. Long-term observational studies describing the natural history of 'mild' PHPT suggest that even though biochemistry may be relatively stable in the majority, bone mineral density (BMD) does decline after approximately 10 years of observation, whereas significant improvements in BMD are seen following PTX. Recent large European record linkage studies of 'mild PHPT' demonstrate significantly increased all-cause and cardiovascular mortality, similar to rates published for patients with PHPT who meet the NIH surgical criteria. 'Mild' PHPT was also associated with increased admissions for nonfatal cardiovascular disease, renal failure, renal stones, fractures, hypertension, psychiatric disease, cancer and diabetes, suggesting that 'insidious' PHPT may be a more appropriate description, or at least that the term 'mild' should be abandoned. Randomized controlled trials (RCTs) have begun to explore the benefits of PTX in this condition, demonstrating improvements in BMD and some psychiatric outcomes at approximately 2 years of follow-up. However, larger, adequately powered, long-term, RCTs will be required to determine whether PTX improves potential long-term morbidity and mortality in patients with PHPT who do not meet standard surgical criteria.

What medical options should be considered for the treatment of primary hyperparathyroidism?

Primary hyperparathyroidism (PHPT) is a common, often asymptomatic, endocrine disorder characterized by hypercalcaemia in the face of a nonsuppressed parathyroid hormone (PTH) level. For those with symptomatic disease or who meet surgical criteria, parathyroidectomy is the treatment of choice. However, those patients who do not meet surgical criteria or who cannot undergo or refuse surgery must be managed medically. Medical management of PHPT involves continual assessment to determine who will benefit from surgical intervention, replacement of vitamin D, treatment of parathyroid bone disease and management of hypercalcaemia and renal stone disease.

Long-term effects of neridronate and its discontinuation in patients with primary hyperparathyroidism

In patients with primary hyperparathyroidism (PHPT) not suitable for surgical correction, a skeletal protection with bisphosphonates is considered a reasonable option, but the long-term effects after treatment discontinuation are not well known. Sixty postmenopausal women with PHPT were given 400-600 IU vitamin D(3) daily and 100 mg neridronate IV every 2 months for 2 years with 2 additional years of follow-up without antiresorptive therapies. Bone mineral density (BMD) progressively rose by 6.7 ± 7.6% (SD) and by 2.9 ± 4.5% at the spine and femoral neck, respectively. During follow-up, mean BMD progressively fell, but after 2 years it was still 3.9 ± 5.5% higher than baseline values at the spine. Bone alkaline phosphatase and serum C-telopeptide of type I collagen decreased significantly within 6 months (28 and 49% versus baseline, respectively) and rose to baseline values within 6-12 months during follow-up. Serum PTH significantly rose from baseline during treatment, but it remained significantly higher than baseline during follow-up. The PTH changes were significantly correlated with serum 25-hydroxyvitamin D (25OHD) levels. In conclusion, in this study we observed that in patients with mild PHPT treatment with bisphosphonates is associated with the expected changes in bone-turnover markers and that the significant increases of both hip and spine BMD are partially maintained for at least 2 years after treatment discontinuation at the vertebral site. The marked increases in serum PTH levels, particularly in subjects with low 25OHD levels, persist after treatment discontinuation and this raises the suspicion that this might reflect a worsening of PHPT.

Cinacalcet HCl reduces hypercalcemia in primary hyperparathyroidism across a wide spectrum of disease severity

CONTEXT

Primary hyperparathyroidism (PHPT) is characterized by elevated serum calcium (Ca) and increased PTH concentrations.

OBJECTIVE

The objective of the investigation was to establish the efficacy of cinacalcet in reducing serum Ca in patients with PHPT across a wide spectrum of disease severity.

DESIGN AND SETTING

The study was a pooled analysis of data from three multicenter clinical trials of cinacalcet in PHPT.

PATIENTS

Patients were grouped into three disease categories for analysis based on the following: 1) history of failed parathyroidectomy (n = 29); 2) meeting one or more criteria for parathyroidectomy but without prior surgery (n = 37); and 3) mild asymptomatic PHPT without meeting criteria for either above category (n = 15).

INTERVENTION

The intervention in this study was treatment with cinacalcet for up to 4.5 yr.

OUTCOMES

Measurements in the study included serum Ca, PTH, phosphate, and bone-specific alkaline phosphatase, and areal bone mineral density (aBMD). Vital signs, safety biochemical and hematological indices, and adverse events were monitored throughout the study period.

RESULTS

The extent of cinacalcet-induced serum Ca reduction, proportion of patients achieving normal serum Ca (≤10.3 mg/dl), reduction in serum PTH, and increase in serum phosphate were similar across all three categories. Except for decreased aBMD at the total femur indicated for parathyroidectomy group at 1 yr, no significant changes in aBMD occurred. The efficacy of cinacalcet was maintained for up to 4.5 yr of follow-up. AEs were mild and similar across the three categories.

CONCLUSIONS

Cinacalcet is equally effective in the medical management of PHPT patients across a broad spectrum of disease severity, and overall cinacalcet is well tolerated.

Primary hyperparathyroidism: an update

PURPOSE OF REVIEW

Primary hyperparathyroidism (PHPT) is a constantly evolving disease. As more evidence on the cardiovascular and neuropsychiatric manifestations of apparently asymptomatic disease accumulates, and since medical therapeutic options and surgical indications are being further investigated, it is important to review this disease entity to gain a fresh, updated perspective on the current disease phenotype and treatment approach.

RECENT FINDINGS

The pathogenesis of PHPT has not been completely elucidated yet, but some potential culprits, such as gene mutations, growth factors, calcium sensing receptor antibodies, and chronic vitamin D deficiency are being identified. There is increasing evidence that even mild, asymptomatic PHPT is associated with some aspects of cardiovascular and neuropsychiatric dysfunction, but the clinical significance as well as the reversibility with parathyroidectomy of these abnormalities remain to be determined. Medical therapies such as bisphosphonates and calcimimetics are showing some promise in the treatment of PHPT, although surgery remains the only curative intervention. The indications for surgical intervention in patients with asymptomatic PHPT have been recently revised.

SUMMARY

Parathyroidectomy is the treatment of choice for patients with symptomatic PHPT and patients with asymptomatic PHPT who fulfill certain age, bone density, serum calcium, and creatinine criteria. Further research is needed to determine whether patients with prominent cardiovascular and neuropsychiatric manifestations would benefit from such intervention.

New perspectives in the management of primary hyperparathyroidism

Primary hyperparathyroidism (PHPT) is a biochemical syndrome caused by the inappropriate or unregulated overproduction of parathyroid hormone, Leading to hypercalcae-mia. It was previously considered a relatively rare disorder, with clinical manifestations dominated by renal and/or bone disease. However, in modern times the diagnosis is most frequently recognized coincidentally on biochemical testing in patients evaluated for unrelated complaints. Parathyroidectomy is the only curative treatment for PHPT, with improved outcomes in symptomatic patients following this procedure. However, surgical intervention in patients with no clear clinical features remains controversial. The National Institutes for Health (NIH) have developed consensus guidelines giving specific indications for when surgery is recommended in patients with asymptomatic PHPT. This article examines the impact of treatment on asymptomatic PHPT, focusing on bone disease, neurocognitive function, quality of Life, cardiovascular disease and mortality. Medical treatment options, including bisphospho-nates and cinacalcet, are also discussed.

Skeletal effects of interventions in mild primary hyperparathyroidism: a meta-analysis

CONTEXT

Uncertainty exists as to the optimal management and monitoring of the skeletal consequences of mild primary hyperparathyroidism (PHPT).

OBJECTIVE

The aim of this study was to determine the effects of surgical treatment, medical treatment and no treatment on bone mineral density (BMD) in mild PHPT.

DATA SOURCES

Our sources were Medline, EMBASE, and Cochrane CENTRAL prior to January 2009, and abstracts from meetings of international bone and mineral societies from 1987-2008.

STUDY SELECTION

Eligible studies were of at least 1-yr duration and included more than 10 participants with mild PHPT (serum calcium < 12 mg/dl) who had BMD measured by dual-energy x-ray absorptiometry while being observed without intervention, or treated with antiresorptive therapy or surgery. Primary analysis was of studies of up to 2-yr duration. Secondary analysis was of studies with follow-up beyond 2 yr.

DATA EXTRACTION

Data were extracted from the text of the retrieved articles or conference abstracts.

DATA SYNTHESIS

Increases in BMD in response to surgical intervention were comparable to those induced by antiresorptive therapies. Significant bone loss was observed in untreated subjects, but the rates of loss ranged from 0.6-1.0%/yr. Analysis of studies reporting data beyond 2 yr of follow-up demonstrated stable increases in BMD after surgery and stable BMD or slow loss (0.1-0.3%/yr) in untreated PHPT.

CONCLUSIONS

Surgical treatment and antiresorptive therapies increase BMD in mild PHPT to a similar degree, and each represents a reasonable option in a patient with mild PHPT and low BMD. Rapid bone loss does not occur in untreated mild PHPT, such that monitoring of BMD less frequently than every 1-2 yr is reasonable in individuals for whom intervention is not immediately required.

Primary hyperparathyroidism--is mild disease worth treating?

Most patients with primary hyperparathyroidism (PHPT) are asymptomatic at presentation. This presents the dilemma whether to treat surgically or manage by conservative follow-up. This article covers the risks of managing mild PHPT conservatively. Some of these risks are well established, for example worsening of bone disease and increased risk of nephrolithiasis. Others, such as effects on cardiovascular function or the risk of malignancy are more controversial. These factors are critical to decisions relating to surgical or conservative management of mild PHPT.

Medical management of asymptomatic primary hyperparathyroidism: proceedings of the third international workshop

BACKGROUND

Primary hyperparathyroidism (PHPT) is a common endocrine disorder that is frequently asymptomatic. The 2002 International Workshop on Asymptomatic PHPT addressed medical management of asymptomatic PHPT and summarized the data on nonsurgical approaches to this disease. At the Third International Workshop on Asymptomatic PHPT held in May 2008, this subject was reviewed again in light of data that have since become available. We present the results of a literature review of advances in the medical management of PHPT.

METHODS

A series of questions was developed by the International Task Force on PHPT. A comprehensive literature search for relevant studies evaluating the management of PHPT with bisphosphonates, hormone replacement therapy, raloxifene, and calcimimetics was conducted. Existing guidelines and recent unpublished data were also reviewed. All selected relevant articles were reviewed, and the questions developed by the International Task Force were addressed by the Consensus Panel.

RESULTS

Bisphosphonates and hormone replacement therapy are effective in decreasing bone turnover in patients with PHPT and improving bone mineral density (BMD). Fracture data are not available with either treatment. Raloxifene also lowers bone turnover in patients with PHPT. None of these agents, however, significantly lowers serum calcium or PTH levels. The calcimimetic cinacalcet reduces both serum calcium and PTH levels and raises serum phosphorus. Cinacalcet does not, however, reduce bone turnover or improve BMD.

CONCLUSIONS

Bisphosphonates and hormone replacement therapy provide skeletal protection in patients with PHPT. Limited data are available regarding skeletal protection in patients with PHPT treated with raloxifene. Calcimimetics favorably alter serum calcium and PTH in PHPT but do not significantly affect either bone turnover or BMD. Medical management of asymptomatic PHPT is a promising option for those who are not candidates for parathyroidectomy.

Primary hyperparathyroidism and the skeleton

Today, primary hyperparathyroidism (PHPT) in the developed countries is typically a disease with few or no obvious clinical symptoms. However, even in the asymptomatic cases the endogenous excess of PTH increases bone turnover leading to an insidious reversible loss of cortical and trabecular bone because of an expansion of the remodelling space and an irreversible loss of cortical bone due to increased endocortical resorption. In contrast trabecular bone structure and integrity to a large extent is maintained and there may be a slight periosteal expansion. Most studies have reported decreased bone mineral density (BMD) in PHPT mainly located at cortical sites, whereas sites rich in trabecular bone only show a modest reduction or even a slight increase in BMD. The frequent occurrence of vitamin D insufficiency and deficiency in PHPT and increased plasma FGF23 levels may also contribute to the decrease in BMD. The effect of smoking is unsolved. Epidemiological studies have shown that the relative risk of spine and nonspine fractures is increased in untreated PHPT starting up to 10 years before the diagnosis is made. Successful surgery for PHPT normalizes bone turnover, increases BMD and decreases fracture risk based on larger epidemiological studies. However, 10 years after surgery fracture risk appears to increase again due to an increase in forearm fractures. There are no randomized controlled studies (RCTs) demonstrating a protective effect of medical treatment on fracture risk in PHPT. Less conclusive studies suggest that vitamin D supplementation may have a beneficial effect on plasma PTH and BMD in vitamin D deficient PHPT patients. Hormone replacement therapy (HRT) and maybe SERM appear to reduce bone turnover and increase BMD. However, their nonskeletal side-effects preclude their use for this purpose. Bisphosphonates reduce bone turnover and increase BMD in PHPT as in osteoporosis and may be a therapeutical option in selected patients with low BMD. Obviously, there is a need for larger RCTs with fractures as end-points that appraise this possibility. Calcimimetics reduce plasma calcium and PTH in PHPT but has no beneficial effect on bone turnover or BMD. In symptomatic hypercalcaemic PHPT with low BMD where curative surgery is impossible or contraindicated a combination of a calcimimetic and a bisphosphonate may be an undocumented therapeutical option that needs further evaluation.

Current Pharmacological Options for the Management of Primary Hyperparathyroidism

Drugs for treating primary hyperparathyroidism can be divided into two main groups: (i) antiresorptive drugs that inhibit the increased bone turnover, which can be divided into estrogen-like compounds (estrogen, oral contraceptives and selective estrogen receptor modulators [SERMs]), bisphosphonates and calcitonin; and (ii) drugs that interfere with parathyroid hormone (PTH) secretion (currently only cinacalcet is available). No drugs that interfere with PTH action are currently available. Available studies suggest that all classes of drugs are able to lower serum calcium levels. However, calcitonin does so only temporarily. Estrogen-containing compounds (hormone replacement therapy) may be less attractive because of the potential risk of breast cancer, cardiovascular disease and deep vein thromboembolism. Oral contraceptives have not been shown to be able to prevent fractures in the general population, and no data are available on their effect in women with primary hyperparathyroidism. The only SERM marketed for hyperparathyroidism is raloxifene and this has not been associated with an increased risk of breast cancer and cardiovascular diseases, and has been shown to be able to prevent vertebral fractures in postmenopausal women with osteoporosis. Two small trials suggest that raloxifene may increase bone mineral density (BMD) and decrease serum calcium levels in patients with primary hyperparathyroidism. Bisphosphonates have been shown to decrease serum calcium and increase BMD in patients with primary hyperparathyroidism, but PTH levels may increase. Cinacalcet effectively induces a sustained decrease in serum calcium and PTH for up to 1 year. However, BMD does not seem to increase. No data on hard endpoints such as fractures, kidney stones, cardiovascular disease etc. are available for any of the drugs available for the treatment of primary hyperparathyroidism.

Hyperparathyroidism in the Elderly Patient

Primary hyperparathyroidism is a common metabolic bone disease and currently presents a significant management dilemma. Most of the patients have few relevant symptoms and surgical parathyroidectomy offers the prospect of cure with freedom from the risk of long-term complications or the need for a follow-up. However, there is a natural reluctance to subject elderly patients to an operation where the balance of advantage is less clear. Advances in parathyroid imaging resulting in a greater use of targeted or focused parathyroidectomy has opened the way for the inclusion of less fit patients into the potentially operable category. However, there is still debate about whether these newer imaging techniques are sufficiently helpful and cost effective to warrant their use in all patients who may need parathyroid surgery. This has stimulated a debate about the indications for parathyroidectomy in the elderly and whether advances in medical therapy, which offset the end organ effects of excess parathyroid hormone, are of sufficient benefit to counteract this trend towards greater surgical intervention. These considerations mean that it is not possible to consider the merits of pharmacological therapy for primary hyperparathyroidism without reviewing the relative merits of minimally invasive and conventional surgery.

Update on genetic and clinical aspects of primary hyperparathyroidism

Primary hyperparathyroidism (pHPT) is a common endocrine disorder that predominantly affects postmenopausal women. It is mostly caused by solitary tumours within the parathyroid glands. Although the pathophysiology of pHPT is still incompletely understood, recent studies provide new clues on the development and cellular growth of tumours within the parathyroids associated with hypersecretion of parathyroid hormone and hypercalcaemia. The natural course of pHPT is rather benign. Nowadays, it has become an oligo- or asymptomatic disease often only detected by routine blood tests. These facts raise the question whether to perform parathyroidectomy on oligo- and asymptomatic patients with pHPT or whether it is possible to monitor these patients without surgery. The aim of this article is to review the literature as regards (i) the pathophysiological mechanisms that underlie parathyroid neoplasia and (ii) the defective calcium-sensing in patients with pHPT (iii) environmental and/or genetic risk factors that predispose to or promote parathyroid neoplasia, as well as (iv) alternative approaches to treat oligo- and asymptomatic patients with pHPT medically.

Raloxifene lowers serum calcium and markers of bone turnover in postmenopausal women with primary hyperparathyroidism

Estrogen replacement therapy (ERT) decreases total serum calcium by about 0.5 mg/dl in postmenopausal women with primary hyperparathyroidism (PHPT). We investigated the ability of raloxifene, which has skeletal antiresorptive properties similar to those of ERT, to decrease serum calcium concentrations and markers of bone turnover in PHPT. Eighteen postmenopausal women with asymptomatic PHPT were randomized to 8 wk of raloxifene (60 mg/d) or placebo, followed by a 4-wk washout. At baseline, the groups were well matched. The calcium concentration decreased significantly by 8 wk of raloxifene administration (10.8 +/- 0.2 to 10.4 +/- 0.2 mg/dl; P < 0.05), as did markers of bone resorption and formation [osteocalcin, 11.4 +/- 1.6 to 9.9 +/- 1.6 nmol/liter (P < 0.05); serum N-telopeptide, 21.2 +/- 3.4 to 17.3 +/- 2.8 nmol bone collagen equivalents/liter (P < 0.05)]. Four weeks after raloxifene was discontinued, indices were indistinguishable from baseline. Raloxifene administration did not affect serum PTH, 1,25-dihydroxyvitamin D, total alkaline phosphatase, or urinary calcium excretion. Calcium and bone marker changes were therefore similar to those observed with ERT in PHPT. This short-term study suggests that raloxifene may be a useful approach to the treatment of postmenopausal women with mild PHPT.

Association of polymorphic alleles of the calcium-sensing receptor gene with the clinical severity of primary hyperparathyroidism

OBJECTIVE

Primary hyperparathyroidism (pHPT) is a heterogeneous disease in its clinical course and severity. Previous studies have suggested an association between the clinical severity of pHPT and the genotypes of vitamin D receptor, oestrogen receptors and PTH molecules. The Ca-sensing receptor (CaR) is activated by an extracellular calcium ion and controls PTH secretion, and thus polymorphisms of CaR might be associated with the magnitude of PTH secretion and the clinical severity of pHPT. In this study, we examined the relationship between CaR polymorphisms and biochemical markers in pHPT patients.

METHODS

We analysed 105 Japanese pHPT patients (85 females and 20 males; mean age 55.6 +/- 14.0 years). We determined the CaR genotypes of G990R and intron 5 polymorphisms with genomic DNA extracted from peripheral lymphocytes. The intron 5 polymorphism was defined as T/T, T/C and C/C.

RESULTS

In the G990R polymorphism, serum levels of both intact PTH and alkaline phosphatase (ALP) were significantly higher and the serum level of phosphorus was significantly lower in the RR group than in the GG group. In the intron 5 polymorphism, the T/T group showed significantly lower serum levels of intact PTH and Ca. Furthermore, patients with both the codon 990 RR and the intron 5 C allele (the RRC(+) group) had significantly higher serum levels of intact PTH and ALP than did the other patients.

CONCLUSIONS

The present study is the first to show that CaR polymorphisms of G990R and intron 5 were closely associated with the magnitude of PTH secretion and/or PTH degradation as well as the clinical severity in pHPT patients.

Childbearing and the risk of parathyroid adenoma--a dominant cause for primary hyperparathyroidism

OBJECTIVES

To explore possible associations between the reproductive history amongst women and the risk of parathyroid adenoma (PA).

DESIGN

Two nationwide Swedish registries. The Fertility Register included data on more than 3.4 million livebirths between 1943 and 1992 amongst Swedish females born 1925-72. The Cancer Register encompasses more than 1800 women with a diagnosis of PA 1960 until 1992.

SETTING

All women resident in Sweden 1960-92.

SUBJECTS

Cases were all 1800 women born 1925-72 reported to the Swedish Cancer Registry with a histopathological diagnosis of PA. Five controls were selected at random for each case by matching for the month and year of birth. Conditional logistic regression was used to estimate relative risks of PA.

MAIN OUTCOMES

Parathyroid adenoma.

RESULTS

High parity (four or more live births) was associated with an increased risk of PA. Amongst women with a diagnosis of PA before menopause (i.e. the age of 50 years) there was an increased risk of PA with younger age at first childbirth. Nulliparous women were at increased risk for PA before menopause, and at decreased risk after menopause.

CONCLUSIONS

There is an association between childbearing and the risk of PA, which has not previously been demonstrated, but the underlying biological mechanisms remain to be determined.

Effects of oral alendronate in elderly patients with osteoporosis and mild primary hyperparathyroidism

In a large proportion of the patients with primary hyperparathyroidism (PHPT), a variable degree of osteopenia is the only relevant manifestation of the disease. Low bone mineral density (BMD) in patients with PHPT is an indication for surgical intervention because successful parathyroidectomy results in a dramatic increase in BMD. However, low BMD values are almost an invariable finding in elderly women with PHPT, who are often either unwilling or considered unfit for surgery. Bisphosphonates are capable of suppressing parathyroid hormone (PTH)-mediated bone resorption and are useful for the prevention and treatment of postmenopausal osteoporosis. In this pilot-controlled study, we investigated the effects of oral treatment with alendronate on BMD and biochemical markers of calcium and bone metabolism in elderly women presenting osteoporosis and mild PHPT. Twenty-six elderly patients aged 67-81 years were randomized for treatment with either oral 10 mg alendronate on alternate-day treatment or no treatment for 2 years. In the control untreated patients a slight significant decrease was observed for total body and femoral neck BMD, without significant changes in biochemical markers of calcium and bone metabolism during the 2 years of observation. Urine deoxypyridinoline (Dpyr) excretion significantly fell within the first month of treatment with alendronate, while serum markers of bone formation alkaline phosphatase and osteocalcin fell more gradually and the decrease became significant only after 3 months of treatment; thereafter all bone turnover markers remained consistently suppressed during alendronate treatment. After 2 years in this group we observed statistically significant increases in BMD at lumbar spine, total hip, and total body (+8.6 +/- 3.0%, +4.8 +/- 3.9%, and +1.2 +/- 1.4% changes vs. baseline mean +/- SD) versus both baseline and control patients. Serum calcium, serum phosphate, and urinary calcium excretion significantly decreased during the first 3-6 months but rose back to the baseline values afterward. Increase in serum PTH level was statistically significant during the first year of treatment. These preliminary results may make alendronate a candidate as a supportive therapy in patients with mild PHPT who are unwilling or are unsuitable for surgery, and for whom osteoporosis is a reason of concern.

Medical approaches to primary hyperparathyroidism

Medical therapy is useful in cases of acute primary hyperparathyroidism, patients with recurrent disease, and parathyroid carcinoma. Among the therapeutic agents that have been employed, oral phosphate, bisphosphonates, and estrogens have been successful. The newly described calcimimetic agents directly block secretion of parathyroid hormone from the glands and offer an important new approach to medical therapy of primary hyperparathyroidism.

Skeletal effects of parathyroid hormone infusion in ovariectomized rats with or without estrogen repletion

We employed skeletally matured rats to study changes in biochemical markers of bone turnover, bone mineral density (BMD), and bone biomechanics produced by continuous elevation of parathyroid hormone (PTH) in estrogen-deplete and -replete rodents. Ninety-six 7-month-old virgin female rats were divided randomly into 12 groups (n = 8) and treated as follows. One group was killed on the day of surgery. The remaining groups were either bilaterally ovariectomized (Ovx) or sham-operated and left untreated for 8 weeks, at which point, two groups, one sham and one Ovx, were killed. The remaining nine groups were treated for 2 weeks or 4 weeks. One sham and two Ovx groups received subcutaneous implants of Alzet miniosmotic pumps with vehicle for PTH. Two Ovx groups were given pumps with vehicle as well as a subcutaneous implant of 17beta-estradiol, which delivered 10 microg/kg per day. Two Ovx groups were implanted with rat PTH(1-34) in Alzet miniosmotic pumps, which delivered 30 microg PTH/kg per day. Two Ovx groups were implanted with both estradiol pellets and PTH-loaded pumps. One group of Ovx animals from each treatment was killed after 2 weeks and the other after 4 weeks. Biochemical markers of bone turnover, serum osteocalcin and urinary free pyridinoline, BMD, and mechanical strength of excised bones were measured. As expected, there was a significant increase in N-terminal PTH and serum calcium levels in all PTH infusion groups. Both serum osteocalcin and urinary pyridinoline showed a rapid increase within the first 2 weeks of the PTH infusion and remained elevated at week 4. In estrogen-replete groups, osteocalcin increased by week 2 of PTH infusion but pyridinoline did not increase until week 4. BMD of the distal and proximal femur showed the expected decrease 8 weeks after ovariectomy but did not exhibit any further changes during the 4 weeks of treatment with vehicle. Four weeks of PTH infusion in Ovx animals resulted in BMD loss at the midshaft, distal, and proximal regions of the femur. Estrogen repletion by itself, beginning 8 weeks after ovariectomy, produced no change in BMD at any site when compared with from Ovx vehicle-treated rats. Estrogen repletion in PTH-infused Ovx animals resulted in significant improvements of BMD comparable with sham-operated animals at all three femoral regions. The indentation test at the cancellous bone of the distal femur, three-point bending test at the midshaft femur, and cantilever bending test at the femoral neck showed that the changes in mechanical strength in these sites were consistent to the changes found in BMD. Our results showed that (1) continuously elevated levels of PTH induced additional loss of BMD in estrogen-deficient animals beyond the rapid bone loss phase associated with ovariectomy, (2) estrogen repletion, given by implant, to PTH-infused Ovx animals, reversed these BMD changes increasing BMD to levels comparable with estrogen-sufficient rats, and (3) these changes were reflected in the mechanical strength determined at these sites. These results lend experimental support that hormone replacement therapy may benefit bone health in postmenopausal women with primary hyperparathyroidism (PHPT). In addition, it raises the possibility that a continuous elevation of PTH could exert anabolic effects on skeletal tissue if its catabolic component can be minimized.

17beta-estradiol potently suppresses cAMP-induced insulin-like growth factor-I gene activation in primary rat osteoblast cultures

Insulin-like growth factor-I (IGF-I) is a key factor in bone remodeling. In osteoblasts, IGF-I synthesis is enhanced by parathyroid hormone and prostaglandin E2 (PGE2) through cAMP-activated protein kinase. In rats, estrogen loss after ovariectomy leads to a rise in serum IGF-I and an increase in bone remodeling, both of which are reversed by estrogen treatment. To examine estrogen-dependent regulation of IGF-I expression at the molecular level, primary fetal rat osteoblasts were co-transfected with the estrogen receptor (hER, to ensure active ER expression), and luciferase reporter plasmids controlled by promoter 1 of the rat IGF-I gene (IGF-I P1), used exclusively in these cells. As reported, 1 microM PGE2 increased IGF-I P1 activity by 5-fold. 17beta-Estradiol alone had no effect, but dose-dependently suppressed the stimulatory effect of PGE2 by up to 90% (ED50 approximately 0.1 nM). This occurred within 3 h, persisted for at least 16 h, required ER, and appeared specific, since 17alpha-estradiol was 100-300-fold less effective. By contrast, 17beta-estradiol stimulated estrogen response element (ERE)-dependent reporter expression by up to 10-fold. 17beta-Estradiol also suppressed an IGF-I P1 construct retaining only minimal promoter sequence required for cAMP-dependent gene activation, but did not affect the 60-fold increase in cAMP induced by PGE2. There is no consensus ERE in rat IGF-I P1, suggesting novel downstream interactions in the cAMP pathway that normally enhances IGF-I expression in skeletal cells. To explore this, nuclear extract from osteoblasts expressing hER were examined by electrophoretic mobility shift assay using the atypical cAMP response element in IGF-I P1. Estrogen alone did not cause DNA-protein binding, while PGE2 induced a characteristic gel shift complex. Co-treatment with both hormones caused a gel shift greatly diminished in intensity, consistent with their combined effects on IGF-I promoter activity. Nonetheless, hER did not bind IGF-I cAMP response element or any adjacent sequences. These results provide new molecular evidence that estrogen may temper the biological effects of hormones acting through cAMP to regulate skeletal IGF-I expression and activity.