No. Coconut oil is claimed to help with numerous health conditions, including an underactive thyroid, weight loss, heart disease and Alzheimer's disease. But there's little to no evidence supporting any of these claims.
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. If necessary, they can recommend appropriate treatment, which may include thyroid hormone therapy.
If you've already been diagnosed with an underactive thyroid, it's important to take your thyroid replacement hormone (levothyroxine) as directed by your doctor. There is no cure for an underactive thyroid. However, the condition can be successfully managed with levothyroxine (Synthroid, Levo-T, others).