Long term use of LNG-IUS (Mirena) does not cause loss of bone mineral density (BMD) in women and is safe to use.
The Mirena IUS is fully funded in New Zealand. One case report1 reported low levels of oestrogen and loss of BMD in a 29-year-old woman who had had a Mirena in situ for 6 years. There was speculation that the cause was disruption of the hypothalamic-gonadal axis. Cohort studies have failed to support such a link.2,3
The Mirena works by prevention of implantation not suppression of ovulation. There is no contraindication to Mirena in women at risk of low BMD, e.g. with eating disorders.4
This Gem was written by Dr Orna McGinn, Clinical Director Primary Care Women’s Health, Auckland District Health Board.