No. The misconception that coconut oil can cure underactive thyroid (hypothyroidism) arose years ago, after publication of a book touting the beneficial effects of coconut oil. However, there is no evidence that coconut oil stimulates thyroid function.
If you have signs or symptoms of hypothyroidism — such as increased sensitivity to cold, unexplained weight gain or fatigue — consult your doctor. He or she can test your thyroid function and, if necessary, recommend appropriate treatment, which may include thyroid hormone therapy.