I assume you have corrected the hypothyroidism -- it may take several months to get the weight off (and lots of hard work). I don't think biotin significantly alters metabolism.
Biotin is involved to some degree in metabolism, so say some experts in
the nutritional field. I personally think if so, it's minor, and part of a cluster
of things that could help.
Ref. Prevent Cancer Now/ Colgan Institute
New Nutrition/Colgan Institute