Rarely. Doing a search on the medical literature, it seems that problems with thyroid function are rare, but can occur. The severity and frequency of these problems is not clear. If you suspect a problem, contact your primary doctor, as some routine lab work can diagnose hypo or hyperthyroidism. The good news is that most of the reported problems with Accutane seem reversible. Best wishes!
Very possibly. Many practitioners have noted an increased risk of thyroid disorders in people who are on, or have been on accutane.