We were told in Oakland that vitamin D and zinc - each on their own contribute to growth in thalassemia.  
When taken in combination they have a greater effect.  This applies also to bone density. 
With some increase in vitamin D little A experienced increase in bone density.  He was in low normal range in 2009 - and in 2010 his bone density was even better.  Since our last visit, he has taken 50,000IU of vitamin D for 6 weeks - and he is now on a maintenance dose (I give him 3000IU a day).  He is also on 50mg of zinc every second day.  With this combination we are hoping to see a further increase in bone density.  Since taking this combination his height has increased from 136cm to 138.2cm from August 20th to December 8th.  We hope to see a lot of growth before our appointment in August.  
I highly recommend this to all thals.  
Sharmin