title: The effects of L-thyroxin replacement therapy on bone minerals and body composition in hypothyroid children.
abstract: BACKGROUND
  Prolonged treatment with levothyroxine 4 (L-T4) is a well known risk factor for osteoporosis. Patients on L-T4 replacement occasionally have a subnormal TSH, which carries a risk of development of bone loss. Thyroid hormones directly affect bone cells, stimulating osteoclastic and osteoblastic activity with a predominance of bone resorption and decrease of bone mineral density (BMD).
  
  
  METHODS
  The study included 35 hypothyroid patients with mean age 11.57 ±5.06, while 26 age- and sex-matched children served as controls. Dual energy X-ray absorptiometry (DXA) was done to detect the bone mineral density (BMD), bone mineral content (BMC) and Z score in lumbar and femur neck regions. Body composition was also studied by DXA. Calcium, phosphorus, osteocalcin as a bone formation marker, osteoprotegerin as an indicator of osteoclast activity and urinary deoxypyridinoline as a bone collagen breakdown marker were assessed.
  
  
  RESULTS
  No significant differences were detected in lumbar Z score (-0.12 ±0.66) and femur Z score (-0.17 ±0.58) compared to controls (-0.33 ±0.74 and -0.21 ±0.53 respectively). Bone mineral density and BMC were not significantly different from controls. No significant difference was detected between cases and controls in body composition. A positive correlation was detected between BMD and age (r=0.857, p<0.01), and with the period of treatment (r=0.766, p<0.01). A positive correlation was found between BMD and total body fat (r=0.693, p<0.01), and with abdominal fat (r=0.667, p<0.01).
  
  
  CONCLUSIONS
  Levothyroxine 4 treatment in hypothyroid children does not alter bone metabolism and body composition.
authors.affiliation: Department of Paediatrics, National Research Centre, Cairo, Egypt.
authors.forename: Hassan M
authors.initials: HM
authors.lastname: Salama
authors.forename: Soha A
authors.initials: SA
authors.lastname: El-Dayem
authors.forename: Hala
authors.initials: H
authors.lastname: Yousef
authors.forename: Ashraf
authors.initials: A
authors.lastname: Fawzy
authors.forename: Laila
authors.initials: L
authors.lastname: Abou-Ismail
authors.forename: Dalia
authors.initials: D
authors.lastname: El-Lebedy