Objectives Animal and in vitro studies suggest that parathyroid hormone (PTH) may affect articular cartilage. However, little is known of the relationship between PTH and human joints in vivo.
Setting Barwon Statistical Division, Victoria, Australia.
Participants 101 asymptomatic women aged 35–49 years (2007–2009) and without clinical knee osteoarthritis, selected from the population-based Geelong Osteoporosis Study.
Risk factors Blood samples obtained 10 years before (1994–1997) and stored at −80°C for random batch analyses. Serum intact PTH was quantified by chemiluminescent enzyme assay. Serum 25-hydroxyvitamin D (25(OH)D) was assayed using equilibrium radioimmunoassay. Models were adjusted for age, bone area and body mass index; further adjustment was made for 25(OH)D and calcium supplementation.
Outcome Knee cartilage volume, measured by MRI.
Results A higher lnPTH was associated with reduced medial—but not lateral—cartilage volume (regression coefficient±SD, p value: −72.2±33.6 mm3, p=0.03) after adjustment for age, body mass index and bone area. Further sinusoidal adjustment (−80.8±34.4 mm3, p=0.02) and 25(OH)D with seasonal adjustment (−72.7±35.1 mm3, p=0.04), calcium supplementation and prevalent osteophytes did not affect the results.
Conclusions A higher lnPTH might be detrimental to knee cartilage in vivo. Animal studies suggest that higher PTH concentrations reduce the healing ability of cartilage following minor injury. This may be apparent in the presence of increased loading, which occurs in the medial compartment, placing the medial cartilage at higher risk for injury.
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Contributors SLB, JAP, FMC and AEW designed the study, while SLB, JAP and AEW conducted the study. SLB and JAP collected the data. SLB measured the knee structures. SLB, JAP, FMC, GCN and AEW analysed the data, whereas SLB, JAP, FMC, MAK, GCN and AEW interpreted the data. SLB and AEW drafted the manuscript, while SLB, JAP, FMC and AEW revised the content of the manuscript. SLB, JAP, FMC, MAK, GCN and AEW approved the final version of the manuscript. All authors had full access to the data (including statistical reports and tables) and take responsibility for the integrity of the data and the accuracy of the data analysis.
Competing interests All authors have completed the Unified Competing Interest form at http://www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare that (1) no author has had any relationships in the past 3 years with companies that might have interest in the submitted work; (2) their spouses, partners or children have no financial relationships that may be relevant to the submitted work; and (3) no author has any non-financial interests that may be relevant to the submitted work.
Patient Consent Obtained.
Ethics approval Barwon Health human research ethics committee and Monash University human research ethics committee.
Provenance and peer review Not commissioned; externally peer reviewed.