Hello.My name is dr Dorina Gurabardhi. Hair loss is a common side effect of thyroid disease, but it s not a permanent problem as long as you get the treatment you need. The hair follicles follow a natural cycle of hair growth and resting phases. At any given time, most of your hair is growing while only a small portion of it is resting. But when changes in the body throw off that cycle, too much hair rests at one time and not enough grows, resulting in excessive hair loss, thinning hair, or balding.Thyroid problems include both an underactive thyroid gland (hypothyroidism) and an overactive thyroid gland (hyperthyroidism)can cause hair loss. Taking the hormone levothyroxine to treat an underactive thyroid can contribute to some hair loss, among other side effects, but this seems to be more common within the first month of treatment. Healthy hormone levels mean healthy hair growth. So you need to measure the hormone level and than to fix the dosage of the medicament. Hope this answer was helpful.Thanks