Hypothyroidism is a condition that occurs when your thyroid gland doesn’t produce enough thyroid hormones.

There are many glands in the body; the thyroid gland is the small butterfly-shaped organ at the base of your neck that makes hormones that regulate your metabolism — which affects how the body uses energy — and other processes.

While your body goes through hormonal changes every day (hello, mood swings!), big dips like those that occur during hypothyroidism can signal danger, as a lack of thyroid hormone production causes the body’s functions to slow down.

Not to mention, an underactive or overactive thyroid(called hyperthyroidism) can affect your waistline. People with hypothyroidism experience a slower metabolic rate, which is generally associated with some amount of weight gain, about 5 to 10 pounds, usually due to accumulation of salt and water in the body.