title: Bone mineral density in adolescent females treated with L-thyroxine: a longitudinal study.
abstract: It has been suggested that chronic treatment with L-thyroxine (L-T4) could be implicated in reducing bone mineral density (BMD). The purpose of this longitudinal study was to determine whether appendicular and axial BMD is decreased by L-T4 treatment in adolescent girls. Thirteen adolescent girls with subclinical hypothyroidism caused by chronic lymphocytic thyroiditis were enrolled in the study at the median age of 13.4 years (range 9.2-18.1 years). L-T4 was administered in a single dose of 1-5 micrograms/kg daily. BMD was evaluated at the distal one-third of the non-dominant radius by single photon absorptiometry (SPA) and at the lumbar spine (L2-4) by dual energy X-ray densitometry (DEXA). Osteocalcin levels were measured to assess bone turnover before and during L-T4 treatment. Before the start of therapy, mean BMD at both the radial and lumbar level was not significantly different from that of a control group (median age 13.0 years; range 9.0-18.5 years). during L-T4 therapy for 2-5 years, BMD did not change at any site. Before treatment, osteocalcin levels were not significantly different from those of controls and did not change during follow up.
  
  
  CONCLUSIONS
  Long-term L-T4 therapy in adolescent girls has no adverse effect on BMD and bone turnover. Our data indicate that attainment of peak bone mass is not impaired by L-T4 administration.
authors.affiliation: Adolescent Medicine Section, Endocrine Unit, II Paediatric Clinic, University of Pisa, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Saggese
authors.forename: S
authors.initials: S
authors.lastname: Bertelloni
authors.forename: G I
authors.initials: GI
authors.lastname: Baroncelli
authors.forename: S
authors.initials: S
authors.lastname: Costa
authors.forename: C
authors.initials: C
authors.lastname: Ceccarelli
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D000365:Age Determination by Skeleton; D015519:Bone Density / Q000187:drug effects*; D002648:Child; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000188:drug therapy*; D008137:Longitudinal Studies; D015675:Osteocalcin / Q000097:blood; D013967:Thyroiditis, Autoimmune / Q000188:drug therapy; D013974:Thyroxine / Q000008:administration & dosage / Q000009:adverse effects*
chemical_list: D015675:Osteocalcin; D013974:Thyroxine