Arthritis & Rheumatism, Volume 60,
October 2009 Abstract Supplement

The 2009 ACR/ARHP Annual Scientific Meeting
Philadelphia October 16-21, 2009.


The Longitudinal Relationship Between Intact Parathyroid Hormone Levels and BMD Loss: The Osteoporotic Fractures in Men (MrOS) Study

Curtis1,  Jeffrey R., Ewing2,  Susan, Bauer3,  Douglas C., Cawthon4,  Peggy, Judd5,  Suzanne, Haney6,  Elizabeth, Ishani7,  Areef

University of Alabama at Birmingham, Birmingham, AL,
San Francisco Coordinating Center, San Francisco, CA,
University of California at San Francisco, San Francisco, CA,
California Pacific Medical Center, San Francisco, CA,
UAB, Birmingham, AL,
Oregon Health and Science University. Portland, OR,
University of Minnesota, Minneapolis, MN

Purpose:

The longitudinal effect of intact parathyroid hormone (iPTH) levels on hip bone mineral density (BMD) loss in older men has been minimally studied. We evaluated the relationship with a particular interest in conditions associated with increased iPTH including low total serum 25(OH)D and decreased renal function.

Method:

We selected a random sample of 1477 community-dwelling men age >= 65 yrs participating in MrOS with baseline iPTH data for analysis. Of these, 1144 had at least 2 BMD measurements at the femoral neck (FN) and total hip (TH) over mean follow-up of 4.5 years. Men taking osteoporosis medications were excluded (n = 86). Annualized BMD change associated with iPTH quartile was estimated using mixed effects regression models. We measured 25(OH)D using mass spec (Mayo); iPTH using radio-immunoassay (Columbia) and estimated glomerular filtration rate (eGFR) by the MDRD equation. Effect modification was assessed for race, serum 25(OH)D and eGFR. Multivariable models were adjusted for age, study site, weight change over the study period, history of cardiovascular disease, use of loop diuretics, season of blood draw, serum 25(OH)D and eGFR.

Results:

Among the 1058 men eligible for analysis, 33 (3.1%) had iPTH > 65pg/ml and 3 also had serum calcium > 10.2mg/dL. There was a significant relationship between iPTH and BMD loss in Caucasians (Table) but a non-significant relationship in non-Caucasians, although an interaction term for race was not significant (p=0.25). Among Caucasians in the highest quartile of iPTH, the rate of BMD loss was approximately two-fold greater than in the lowest quartile. Results were similar for FN BMD (not shown). There was some evidence for effect modification by eGFR (interaction p-value=0.08). In stratified analysis (Table), men in the highest quartile of iPTH with reduced eGFR (< 60cc/min) had a 1.4 times higher rate of BMD loss compared to the corresponding men with normal eGFR. No effect modification by 25(OH)D was observed (interaction p value=0.95).

Table. Association between iPTH and Total Hip BMD Loss in Caucasian Men

 Quartiles of Intact PTH
Adjusted* Change in Total Hip BMD, %/yrQ1 (<23pg/ml)Q2 (23–29 pg/ml)Q3 (29–38 pg/ml)Q4 (>=38 pg/ml)Adjusted p for trend
Overall-0.25-0.25-0.34-0.520.0003
Stratified Results by eGFR     
eGFR<60 cc/min-0.26-0.27-0.28-0.710.06
eGFR>=60 cc/min-0.24-0.24-0.35-0.490.002
* adjusted for factors described in text

Conclusion:

Older Caucasian men with higher baseline levels of iPTH had greater subsequent BMD loss; many had iPTH values within the accepted laboratory "normal" range. Concomitant reduced renal function further increased the rate of BMD loss. Based upon our results, iPTH < 38pg/ml is more optimal for maintaining BMD.

To cite this abstract, please use the following information:
Curtis, Jeffrey R., Ewing, Susan, Bauer, Douglas C., Cawthon, Peggy, Judd, Suzanne, Haney, Elizabeth, et al; The Longitudinal Relationship Between Intact Parathyroid Hormone Levels and BMD Loss: The Osteoporotic Fractures in Men (MrOS) Study [abstract]. Arthritis Rheum 2009;60 Suppl 10 :864
DOI: 10.1002/art.25944

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