Change in spinal bone mineral density as estimated by Hounsfield units following osteoporosis treatment with romosozumab, teriparatide, denosumab, and alendronate: an analysis of 318 patients.

OBJECTIVE: The purpose of this study was to determine the effect of osteoporosis medications on opportunistic CT-based Hounsfield units (HU). METHODS: Spine and nonspine surgery patients were retrospectively identified who had been treated with romosozumab for 3 to 12 months, teriparatide for 3 to 12 months, teriparatide for > 12 months, denosumab for > 12 months, or alendronate for > 12 months. HU were measured in the L1-4 vertebral bodies. One-way ANOVA was used to compare the mean change in HU among the five treatment regimens. RESULTS: In total, 318 patients (70% women) were included, with a mean age of 69 years and mean BMI of 27 kg/m2. There was a significant difference in mean HU improvement (p < 0.001) following treatment with romosozumab for 3 to 12 months (n = 32), teriparatide for 3 to 12 months (n = 30), teriparatide for > 12 months (n = 44), denosumab for > 12 months (n = 123), and alendronate for > 12 months (n = 100). Treatment with romosozumab for a mean of 10.5 months significantly increased the mean HU by 26%, from a baseline of 85 to 107 (p = 0.012). Patients treated with teriparatide for > 12 months (mean 23 months) experienced a mean HU improvement of 25%, from 106 to 132 (p = 0.039). Compared with the mean baseline HU, there was no significant difference after treatment with teriparatide for 3 to 12 months (110 to 119, p = 0.48), denosumab for > 12 months (105 to 107, p = 0.68), or alendronate for > 12 months (111 to 113, p = 0.80). CONCLUSIONS: Patients treated with romosozumab for a mean of 10.5 months and teriparatide for a mean of 23 months experienced improved spinal bone mineral density as estimated by CT-based opportunistic HU. Given the shorter duration of effective treatment, romosozumab may be the preferred medication for optimization of osteoporotic patients in preparation for elective spine fusion surgery.

Comprehensive outcomes after Roux-en-Y gastric bypass with a near-complete 15-year follow-up.

BACKGROUND: Laparoscopic Roux-en-Y gastric bypass has a well-established safety and efficacy profile in the short and mid-term. Long-term outcomes remain limited in the literature, especially for follow-up periods of >10 years. The purpose of the study is to evaluate the long-term durability and safety of laparoscopic Roux-en-Y gastric bypass over a near-complete 15-year follow-up. METHODS: This is a single-center retrospective cohort study of patients who underwent primary laparoscopic Roux-en-Y gastric bypass between 2008 and 2009 with ≥14-year follow-up. Data collected and analyzed were weight loss, obesity-related medical condition resolution and recurrence, weight recurrence, complication rate, and mortality rate. RESULTS: A total of 264 patients were included. Patients were predominantly female (81.8%), and the mean age and preoperative body mass index were 48.5 ± 12.2 years and 44.9 ± 7.3 kg/m2, respectively. The maximum mean percentage total weight loss achieved at 1 year was 31.5% ± 5.7% and was consistently >20% throughout follow-up. Sustained resolution of obesity-related medical conditions was achieved with a remission rate of 60.8% for type 2 diabetes mellitus, 46.7% for denoted dyslipidemia, and 40% for hypertension. Obesity-related medical condition recurrence was observed with a recurrence rate of 24.1% for type 2 diabetes mellitus, 17.9% for hypertension, and 14.8% for denoted dyslipidemia. Significant factors associated with weight loss were maximum percentage total weight loss and preoperative type 2 diabetes mellitus. Over 15 years, the weight recurrence rate was 51.1%, with predictors of higher preoperative body mass index and preoperative type 2 diabetes mellitus. CONCLUSION: Laparoscopic Roux-en-Y gastric bypass provides sustainable weight loss over a 15-year period, with consistent long-term weight-loss outcomes and resolution of obesity-related medical conditions sustained for ≥10 years after surgery.

Type 2 diabetes remission after Roux-en-Y gastric bypass: a multicentered experience with long-term follow-up.

BACKGROUND: Roux-en-Y gastric bypass (RYGB) is associated with short- and mid-term type 2 diabetes (T2D) remission. Long-term outcomes and predictive parameters associated with remission following RYGB have not been well elucidated. OBJECTIVE: Determining the overall long-term T2D remission rates following RYGB and identifying predictive variables associated with remission. SETTING: Multicentered study including patients who underwent RYGB at 3 tertiary referral centers for bariatric surgery. METHODS: We performed a retrospective cohort study between 2008-2017 to allow a minimum of 5 years of follow-up. We evaluated long-term T2D remission rates and annual T2D clinical and metabolic parameters up to 14 years after surgery. Predictors of remission were assessed using multivariate logistic regression. Patients were divided into 4 groups based on quartiles of total body weight loss percentage (%TBWL) to compare remission rates between groups. RESULTS: A total of 815 patients were included (68.9% female, age 52.1 ± 11.5 yr; body mass index 45.1 ± 7.7 kg/m2) with a follow-up of 7.3 ± 3.8 years. Remission was demonstrated in 51% of patients. Predictors of remission included pre-operative duration of diabetes, baseline HbA1C, insulin use prior to surgery, number of antidiabetic medications and %TBWL (all P < .01). Remission rates were proportionally associated with %TBWL quartile (Q1, 40.9%; Q2, 52.7%; Q3, 53.1%; Q4, 56.1%) (P = .02). CONCLUSIONS: Longer duration and higher severity of T2D were negatively associated with remission while higher %TBWL had a positive association. A significant proportion of patients in all quartiles experienced long-term remission after RYGB with a greater likelihood of remission correlated with greater weight loss.

Opportunistic CT-Based Hounsfield Units Strongly Correlate with Biomechanical CT Measurements in the Thoracolumbar Spine.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: Hounsfield units (HUs) are known to correlate with clinical outcomes, no study has evaluated how they correlate with BCT and DXA measurements. SUMMARY OF BACKGROUND: Low bone mineral density (BMD) represents a major risk factor for fracture and poor outcomes following spine surgery. Dual-energy x-ray absorptiometry (DXA) can provide regional BMD measurements but has limitations. Opportunistic HUs provide targeted BMD estimates; however, they are not formally accepted for diagnosing osteoporosis in current guidelines. More recently, biomechanical computed tomography (BCT) analysis has emerged as a new modality endorsed by the International Society for Clinical Densitometry (ISCD) for assessing bone strength. METHODS: Consecutive cases from 2017-2022 at a single institution were reviewed for patients who underwent BCT in the thoracolumbar spine. BCT-measured vertebral strength, trabecular BMD, and the corresponding American College of Radiology (ACR) Classification were recorded. DXA studies within three months of the BCT were reviewed. Pearson Correlation Coefficients were calculated, and receiver-operating characteristic curves were constructed to assess the predictive capacity of HUs. Threshold analysis was performed to identify optimal HU values for identifying osteoporosis and low BMD. RESULTS: Correlation analysis of 114 cases revealed a strong relationship between HUs and BCT vertebral strength (r=0.69; P<0.0001; R2=0.47) and trabecular BMD (r=0.76; P<0.0001; R2=0.58). However, DXA poorly correlated with opportunistic HUs and BCT measurements. HUs accurately predicted osteoporosis and low BMD (Osteoporosis: C=0.95, 95% CI 0.89-1.00; Low BMD: C=0.87, 95% CI 0.79-0.96). Threshold analysis revealed that 106 and 122 HUs represent optimal thresholds for detecting osteoporosis and low BMD. CONCLUSION: Opportunistic HUs strongly correlated with BCT-based measures, while neither correlated strongly with DXA-based BMD measures in the thoracolumbar spine. HUs are easy to perform at no additional cost and provide accurate BMD estimates at non-instrumented vertebral levels across all ACR-designated BMD categories.

Teriparatide Treatment Increases Hounsfield Units in the Thoracic Spine, Lumbar Spine, Sacrum, and Ilium Out of Proportion to the Cervical Spine.

STUDY DESIGN: This was a retrospective chart review. OBJECTIVE: The objective of this study was to compare the effect of teriparatide on Hounsfield Units (HU) in the cervical spine, thoracic spine, lumbar spine, sacrum, and pelvis. Second, to correlate HU changes at each spinal level with bone mineral density (BMD) on dual-energy x-ray absorptiometry (DXA). SUMMARY OF BACKGROUND DATA: HU represent a method to estimate BMD and can be used either separately or in conjunction with BMD from DXA. MATERIALS AND METHODS: A retrospective chart review included patients who had been treated with at least 6 months of teriparatide. HU were measured in the vertebral bodies of the cervical, thoracic, and lumbosacral spine and iliac crests. Lumbar and femoral neck BMD as measured on DXA was collected when available. RESULTS: One hundred twenty-five patients were identified for analysis with an average age of 67 years who underwent a mean (±SD) of 22±8 months of teriparatide therapy. HU improvement in the cervical spine was 11% (P=0.19), 25% in the thoracic spine (P=0.002), 23% in the lumbar spine (P=0.027), 17% in the sacrum (P=0.11), and 29% in the iliac crests (P=0.09). Lumbar HU correlated better than cervical HU with BMD as measured on DXA. CONCLUSIONS: Teriparatide increased average HU in the thoracolumbar spine to a proportionally greater extent than the cervical spine. The cervical spine had a higher baseline starting HU than the thoracolumbar spine. Lumbar HU correlated better than cervical and thoracic HU with BMD as measured on DXA.

Osteoporosis in spine surgery patients: what is the best way to diagnose osteoporosis in this population?

OBJECTIVE: The goal of this study was to compare different recognized definitions of osteoporosis in patients with degenerative lumbar spine pathology undergoing elective spinal fusion surgery to determine which patient population should be considered for preoperative optimization. METHODS: A retrospective review of patients in whom lumbar spine surgery was planned at 2 academic medical centers was performed, and the rate of osteoporosis was compared based on different recognized definitions. Assessments were made based on dual-energy x-ray absorptiometry (DXA), CT Hounsfield units (HU), trabecular bone score (TBS), and fracture risk assessment tool (FRAX). The rate of osteoporosis was compared based on different definitions: 1) the WHO definition (T-score ≤ -2.5) at total hip or spine; 2) CT HU of < 110; 3) National Bone Health Alliance (NBHA) guidelines; and 4) "expanded spine" criteria, which includes patients meeting NBHA criteria and/or HU < 110, and/or "degraded" TBS in the setting of an osteopenic T-score. Inclusion criteria were adult patients with a DXA scan of the total hip and/or spine performed within 1 year and a lumbar spine CT scan within 6 months of the physician visit. RESULTS: Two hundred forty-four patients were included. The mean age was 68.3 years, with 70.5% female, 96.7% Caucasian, and the mean BMI was 28.8. Fracture history was reported in 53.8% of patients. The proportion of patients identified with osteoporosis on DXA, HUs, NBHA guidelines, and the authors' proposed "expanded spine" criteria was 25.4%, 36.5%, 75%, and 81.9%, respectively. Of the patients not identified with osteoporosis on DXA, 31.3% had osteoporosis based on HU, 55.1% had osteoporosis with NBHA, and 70.4% had osteoporosis with expanded spine criteria (p < 0.05), with poor correlations among the different assessment tools. CONCLUSIONS: Limitations in the use of DXA T-scores alone to diagnose osteoporosis in patients with lumbar spondylosis has prompted interest in additional methods of evaluating bone health in the spine, such as CT HU, TBS, and FRAX, to inform guidelines that aim to reduce fracture risk. However, no current osteoporosis assessment was developed with a focus on improving outcomes in spinal surgery. Therefore, the authors propose an expanded spine definition for osteoporosis to identify a more comprehensive cohort of patients with potential poor bone health who could be considered for preoperative optimization, although further study is needed to validate these results in terms of clinical outcomes.

Hypocalcemia After Bariatric Surgery: Prevalence and Associated Risk Factors.

BACKGROUND: The reported prevalence of hypocalcemia after bariatric surgery ranges from 1% after Roux-en-Y gastric bypass (RYGB) to 25% after bilio-pancreatic diversion-duodenal switch (BPD-DS). OBJECTIVE: We aimed to define the prevalence of post-operative hypocalcemia and identify clinical predisposing factors. SETTING: The study was conducted in an Academic Medical Center, USA. METHODS: Retrospective analysis of all patients undergoing bariatric surgery from May 2008 to December 2014 at Mayo Clinic Rochester, Minnesota was performed. Patients with revision surgeries were excluded. Hypocalcemia was defined as the lowest recorded serum calcium occurring at least 2 weeks post-operatively. RESULTS: Nine hundred ninety-nine patients fulfilled the criteria above. After correction for serum albumin concentration, 36 patients had serum calcium ≤8.9 mg/dl. Mean serum calcium was 8.1 ± 0.6 mg/dl. The prevalence was 1.9% in the RYGB group, 9.3% in the sleeve gastrectomy (SG) group, and 10% in the BPD-DS group. In all three surgical types, patients with hypocalcemia had significantly lower serum albumin and serum 25 (OH) vitamin D concentrations when compared to their normocalcemic counterparts (P < 0.01). The presence of renal insufficiency and vitamin D deficiency was associated with the highest risk of developing hypocalcemia after surgery [OR 16.8 (6.45-47.7) and 7.1(2.9-17.3), respectively]. Pre-operative renal insufficiency increased the odds of developing hypocalcemia by 20-fold. CONCLUSIONS: In our series, hypocalcemia was identified in 3.6% of patients undergoing all bariatric surgery. Patients who are predisposed to developing post-operative hypocalcemia, such as those with pre-operative renal impairment, or post-operative vitamin D deficiency and renal insufficiency, may benefit from increased surveillance and prevention strategies.

Comparison of Clinical Risk Tools for Predicting Osteoporosis in Women Ages 50-64.

OBJECTIVE: The objective of this study was to compare the performance of the US Preventive Services Task Force (USPSTF) recommended WHO Fracture Risk Assessment Tool (FRAX) threshold score of 9.3% (calculated without femoral neck bone density) with the Simple Calculated Osteoporosis Risk Estimate (SCORE), Osteoporosis Self-Assessment Tool (OST), and the Osteoporosis Risk Assessment Instrument (ORAI) to identify osteoporosis in younger women. METHODS: We conducted a retrospective review of women ages 50 to 64 years who underwent dual-energy radiographic absorptiometry (DXA) at our institution over a 6-month period. Scores for the FRAX, ORAI, OST, and SCORE tools were calculated using various thresholds: FRAX ≥9.3%, SCORE ≥6, OST <2, and ORAI ≥9. Sensitivity, specificity, and area under the receiver-operating characteristic curve for detection of densitometric osteoporosis by DXA for each tool were compared. RESULTS: A total of 290 women were identified. Of these, 284 (97.9%) were white, and the mean ± standard deviation age was 56.6 ± 3.4 years. Fifty (17.2%) had osteoporosis of the lumbar spine and/or femoral neck on DXA. Sensitivity, specificity, and area under the receiver-operating characteristic curve for identifying densitometric osteoporosis at the femoral neck and/or spine were 36%, 73%, and 0.55 for FRAX; 74%, 42%, and 0.58 for SCORE; 56%, 69%, and 0.63 for the OST; and 52%, 67%, and 0.60 for the ORAI, respectively. CONCLUSIONS: DXA screening based on the USPSTF-recommended FRAX threshold score of 9.3% has a low sensitivity to identify densitometric osteoporosis in women ages 50 to 64. Lowering the threshold score would increase sensitivity but would also increase the number of women sent for screening DXA. Use of the validated SCORE tool would improve sensitivity to identify osteoporosis in this age group.

Vitamin D in the cancer patient.

PURPOSE OF REVIEW: To briefly review recent work within the vitamin D and cancer field, whereas also providing context relating how these findings may impact clinical care and future research efforts. RECENT FINDINGS: Vitamin D has now been convincingly shown both in vitro and in preclinical animal models to alter the differentiation, proliferation, and apoptosis of cancer cells. Whether vitamin D prevents cancer in humans or limits cancer progression, however, remain open questions. Epidemiologic and observational data relating circulating 25(OH)D levels and cancer risk suggest an inverse relationship for most cancers including breast, colorectal, leukemia and lymphoma, and prostate, although for each malignancy there also exist studies that have failed to demonstrate such an inverse relationship. Likewise, a more recent report failed to confirm a previously reported association of increased pancreatic cancer risk in patients with higher 25(OH)D levels. A large prospective study in which patients aged at least 50 years receive 2000 IU vitamin D3 daily for 5 years, with cancer as a primary endpoint, has recently been launched. SUMMARY: Although much effort has attempted to delineate a causal relationship between vitamin D and a wide array of human cancers, we await large-scale randomized controlled trial data for definitive answers.

Vitamin D deficiency in adults: when to test and how to treat.

Recent evidence for the nonskeletal effects of vitamin D, coupled with recognition that vitamin D deficiency is common, has revived interest in this hormone. Vitamin D is produced by skin exposed to ultraviolet B radiation or obtained from dietary sources, including supplements. Persons commonly at risk for vitamin D deficiency include those with inadequate sun exposure, limited oral intake, or impaired intestinal absorption. Vitamin D adequacy is best determined by measurement of the 25-hydroxyvitamin D concentration in the blood. Average daily vitamin D intake in the population at large and current dietary reference intake values are often inadequate to maintain optimal vitamin D levels. Clinicians may recommend supplementation but be unsure how to choose the optimal dose and type of vitamin D and how to use testing to monitor therapy. This review outlines strategies to prevent, diagnose, and treat vitamin D deficiency in adults.

Adverse effects of bisphosphonates: implications for osteoporosis management.

Bisphosphonates are widely prescribed and highly effective at limiting the bone loss that occurs in many disorders characterized by increased osteoclast-mediated bone resorption, including senile osteoporosis in both men and women, glucocorticoid-associated osteoporosis, and malignancies metastatic to bone. Although they are generally well tolerated, potential adverse effects may limit bisphosphonate use in some patients. Optimal use of bisphosphonates for osteoporosis requires adequate calcium and vitamin D intake before and during therapy. The World Health Organization fracture risk assessment algorithm is currently available to determine absolute fracture risk in patients with low bone mass and is a useful tool for clinicians in identifying patients most likely to benefit from pharmacological intervention to limit fracture risk. This fracture risk estimate may facilitate shared decision making, especially when patients are wary of the rare but serious adverse effects that have recently been described for this class of drugs.

Effect of osteoporotic status on the survival of titanium dental implants.

OBJECTIVES: The aim of this study was to determine whether a diagnosis of osteoporosis affected the survival rate of osseointegrated dental implants. Other variables that were studied were age, arch location of the implant, and smoking status on the effect of dental implant survival. MATERIALS AND METHODS: A retrospective chart review was completed on all women who were 50 years of age or older at the time of dental implant placement at the Mayo Clinic between October 1, 1983, and December 31, 2004. Osteoporotic status was defined on the basis of bone mineral density (BMD) score utilizing World Health Organization criteria. Univariate analyses were performed to evaluate the following independent variables' effect on implant survival: BMD T-score, age, osteoporosis status, arch location of the implant, and smoking status at the time of implant placement. RESULTS: A total of 3,224 implants in 746 female patients 50 years of age or older at the time of implant placement were evaluated. BMD scores within 3 years of implant placement were available for 646 implants (192 patients). In this group, 37 implant failures were noted. The 5-year implant survival rate was 93.8% in the group of patients with BMD scores. In this group of 192 patients, there were 94 (49%) who were not diagnosed with osteopenia or osteoporosis, 57 (29.7%) with a diagnosis of osteopenia, and 41 (21.4%) with a diagnosis of osteoporosis. Patients with a diagnosis of osteoporosis or osteopenia were not significantly more likely to develop implant failure compared to those without such a diagnosis (HR = 1.14, 95% CI = 0.50 to 0.60, P = .76 and HR = 0.98, 95% CI = 0.40 to 2.42, P = .97, respectively). Arch location and BMD score did not have a statistically significant effect on implant survival rates. The only tested variable to demonstrate a significant effect was smoking. Implants in patients who were smokers during the time of implant placement were 2.6 times more likely to fail compared to implants placed in patients who did not smoke (HR = 2.6, 95% CI = 1.20 to 5.63; P = .016). CONCLUSIONS: Based upon the data derived from this retrospective study of 192 women at least 50 years of age at the time of implant placement, the following observations were made: (1) a diagnosis of osteoporosis and osteopenia did not contribute to increased risk of implant failure and (2) implants placed in patients who were smokers at the time of implant placement were 2.6 times more likely to fail than implants placed in nonsmokers. Based on these data, a diagnosis of osteoporosis or osteopenia is not a contraindication to dental implant therapy.

The malabsorptive very, very long limb Roux-en-Y gastric bypass for super obesity: results in 257 patients.

BACKGROUND: For the past 11 years, we have used a malabsorptive form of Roux-en-Y gastric bypass (RYGB), the "very, very long limb" RYGB, for selected patients with BMIs >50 kg/m(2) and in highly selected patients with BMI <50 kg/m(2). This modified distal gastric bypass establishes a 100-cm common channel (for digestion and absorption) and a "very, very" long Roux limb of 400 to 500 cm. METHODS: To determine long-term efficacy and complications, we followed prospectively 257 consecutive patients; 188 (73%) participated in a postoperative survey. RESULTS: Of the patients, 60% were female; overall age (x +/- SD) was 45 +/- 11 years, and BMI was 61 +/- 11 kg/m(2). Operative mortality was 1% with substantive postoperative morbidity occurring in 13%. Eighty-two percent of patients returning the survey an average of 48 months postoperatively (range, 12 to 148 months) lost >50% of excess body weight; BMI at follow-up was 37 +/- 9 kg/m(2). Resolution of comorbidities included diabetes mellitus (94%), hypertension (65%), sleep apnea (48%), and asthma (30%). Side effects included mild food intolerance (82%), occasional loose or watery stools (71%), nephrolithiasis (16%), and symptomatic steatorrhea (5%). Nine patients (4%) who developed or were developing impending protein/calorie malnutrition required proximal relocation of the enteroenterostomy with symptom resolution. CONCLUSIONS: Overall, 90% were satisfied with the operation, and 93% would recommend it to a friend. The very, very long limb RYGB is relatively safe and effective and has acceptable side effects in the treatment of selected patients with super obesity (BMI >50). Because of the possibility of malabsorptive sequelae, patients should be selected based on degree of medical sophistication, insight, and compliance.

Traumatic fracture in a healthy man: benign or pathologic?

OBJECTIVE: To describe the challenge of determining the correct diagnosis in a healthy adult male patient with a recent femoral fracture and a history of multiple bone fractures. METHODS: We present clinical, radiologic, laboratory, and histopathologic details in a patient with a history of recurrent fractures associated with minimal trauma. Moreover, the various types of osteopetrosis are reviewed. RESULTS: A 34-year-old African American man was in his usual state of good health when he fell hard on concrete. Immediately after the fall, he was able to bear weight, although pain prompted him to seek medical care. Besides a personal history of multiple fractures, he had no other medical problems. He had never smoked, denied illicit drug use, and had no family history of bone disorders or recurrent fractures. Findings on physical examination were unremarkable. Radiography disclosed an incomplete femoral fracture and osteosclerosis. Bone survey revealed diffuse, symmetric osteosclerosis of both the axial and the appendicular skeleton. The long bones showed areas of almost complete obliteration of the medullary canal, along with prominent hyperostosis. Additionally, a "bone-within-bone" appearance to the thickened endosteum was noted. A bone scan demonstrated numerous areas of symmetric radiotracer uptake. Laboratory analyses were unremarkable, including a complete blood cell count, electrolytes, serum protein electrophoresis, thyrotropin, and parathyroid hormone. Total alkaline phosphatase was mildly elevated at 162 U/L (normal range, 35 to 130). Seven needles were broken during attempts to perform a bone biopsy. Histologic examination showed normal bone marrow with "woven" bone and areas of primary spongiosa within mature osteoid. Autosomal dominant osteopetrosis type 2 was diagnosed on the basis of his clinical presentation and the radiologic and pathologic findings. CONCLUSION: The preliminary diagnosis for this patient's condition was Paget's disease, and determining the correct diagnosis of osteopetosis prevented the administration of inappropriate therapy. In addition, this case report reminds the clinician that genetic disease may manifest in adulthood.

Role of parathyroid hormone in mediating age-related changes in bone resorption in men.

Osteoporosis in men is an important and growing public health problem. While there has been extensive work done on defining the mechanism(s) of the age-related increase in bone resorption in women, our knowledge regarding the pathogenesis of bone loss in elderly men is still incomplete. We previously demonstrated that the age-related increase in serum PTH contributes substantially to the increased bone resorption in elderly women, since suppression of PTH levels by an intravenous calcium infusion decreased bone resorption markers to a greater extent in elderly compared to premenopausal women. In the present study, we tested the hypothesis that the comparable increase in PTH levels in elderly men (age 70-78 years) was driving bone resorption to a greater extent in these men than in younger men (age 40-50 years). PTH secretion was suppressed by an intravenous calcium infusion and the corresponding changes in the bone resorption marker, urine N-telopeptide of type I collagen (NTx) were assessed. In contrast to our previous findings in pre- versus postmenopausal women, suppression of PTH secretion in elderly men did not result in a greater decrease in urine NTx excretion than in the younger men (change in NTx excretion in the elderly men, -2.79+/-1.99 nmol/mmol Cr, versus that in the younger men, -5.07+/-1.39 nmol/mmol Cr, P=0.356). Collectively, these data suggest that the relationship between the age-related increase in serum PTH levels and bone resorption differs between elderly men and women. Since both estrogen and testosterone can attenuate the bone resorbing effects of PTH, it is possible that this difference may be due to the much milder degree of sex steroid deficiency in elderly men as compared to postmenopausal women.