Why am I losing hair?

Im a 19 yr old male who weighed 215 and now weigh 165. I recently lost about 60 pounds during the summer(in about 2 months) by drastically cutting down what I ate but didn't notice any thinning of the hair until September or early October. I may have hyperthyroidism aswell. Since then I have been taking vitamins and eating pretty healthy but my hair still falls out and has become inceasingly thin on top of my head. Is this male pattern baldness or from weightloss? When will my hair start growing back and are there any suggestions as to what this may be?