title: Similar efficacy of low and standard doses of transdermal estradiol in controlling bone turnover in postmenopausal women.
abstract: OBJECTIVE
  To investigate the effects of a low transdermal estradiol dose on bone metabolism and to compare it with both the standard dose and absence of treatment.
  
  
  METHODS
  In this study performed in a third-level academic center, 66 healthy postmenopausal women underwent hormone therapy (HT) with patches containing estradiol at standard (0.050 mg/day, HT50, 33 women) or low dosage (0.025 mg/day, HT25, 33 women) and 70 women were without treatment (NT). The values (mean of three samples) of several bone biochemical parameters were compared between groups after adjusting for confounding factors. Bone mineral density (BMD) was assessed (by dual-energy X-ray absorptiometry) in the spine and hip in all cases, and a second densitometry scan was performed in 44 women.
  
  
  RESULTS
  Bone turnover markers tended to show lower values in the treated groups, but significance was restricted to total alkaline phosphatase (NT vs. HT25, p < 0.05) and cross-linked N-telopeptides of type I collagen (NTX) (NT vs. HT25, p < 10(-6); NT vs. HT50, p < 10(-5)). The loss of BMD observed in NT women, as assessed by the annual percentage change, was blocked in both the HT25 and HT50 women. No significant differences were detected between both HT groups.
  
  
  CONCLUSIONS
  Low and standard dosages of transdermal estradiol were equally effective in controlling bone metabolism, as assessed by turnover markers. Additionally, NTX was confirmed as the most sensitive marker for detecting changes in bone resorption.
authors.affiliation: Research Unit, Hospital Clínico, University of Valencia, Spain.
authors.forename: Miguel Angel
authors.initials: MA
authors.lastname: García-Pérez
authors.forename: Jane
authors.initials: J
authors.lastname: Moreno-Mercer
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Tarín
authors.forename: Antonio
authors.initials: A
authors.lastname: Cano
mesh_terms: D000469:Alkaline Phosphatase / Q000097:blood; D000704:Analysis of Variance; D015415:Biomarkers / Q000097:blood / Q000652:urine; D015519:Bone Density / Q000187:drug effects*; D024042:Collagen Type I / Q000652:urine; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000008:administration & dosage*; D015914:Estrogen Replacement Therapy / Q000379:methods; D005260:Female; D006801:Humans; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000517:prevention & control; D010455:Peptides / Q000652:urine; D017698:Postmenopause / Q000187:drug effects*
chemical_list: D015415:Biomarkers; D024042:Collagen Type I; D010455:Peptides; C052929:collagen type I trimeric cross-linked peptide; D004958:Estradiol; D000469:Alkaline Phosphatase