You need to assess Thyroid Issue.
One of the three Thyroid Hormones, Calcitonin, helps regulate Calcium, as does the little organ behind the Thyroid, the Parathyroid, Calcium and Phosphorus.
Any possible skew whiff regulation of those Bone minerals, could cause reduced Bone density, possibly entering into Osteopenia country at some point, making exercise more risky, in respect of possible fractures.
If your Thyroid med is and should be listed on the recepticle, as a certain doseage, then you should be able to safely take it, without over doing it, as you'll know what is the right thing to do.
you could also double check on this site
If you do start experiencing any isdues resulting from Thyroid problems, you'd defintiely need to reassess the situation more.
If you felt you might have Bone density issues, you could have it tested with either a T-Score or Z-Score test.
Z-score is based on the average bone density, for someone of about your age and gender.
T-score is based on the bone density of a healthy 30 year old man. Not sure why but it is.
If you are between -1 and -2.5, you have Osteopenia. lower thsn -2.5 is Osteoperosis, and above -1 up to 0, (don't think it goes higher than that, but it could), is healthy.
So that is something to consider.
I'm sure you'll get where you want to be in time though.
Good luck yeah