Causes of Hypothyroidism

by Yumhee Park Content Producer

Hypothyroidism, also known as an underactive thyroid, is when the thyroid doesn’t produce enough hormones resulting in a chemical imbalance in the body and greatly affecting metabolism. This can cause multiple health problems that can be difficult to diagnose. The thyroid is located in the front of the neck and is part of the endocrine system. Here are some common and less common causes of hypothyroidism.

Illustration of germs.

Autoimmune disease

Diseases like Hashimoto’s disease where the immune system attacks the thyroid, can often cause hypothyroidism. This disease is the most common cause of hypothyroidism in the U.S. Other autoimmune diseases can act in a similar way and cause the condition.

Surgical instruments.

Thyroid surgery

Undergoing surgery to remove parts or all of your thyroid gland can reduce or completely stop thyroid hormone production and lead to hypothyroidism.

Radiation therapy treatment.

Radiation therapy

Radiation therapy is used to treat cancers. Unfortunately, if radiation therapy is used on the head or neck, the radiation could affect the thyroid and cause hypothyroidism.

Prescription drug bottles sitting on countertop.


Certain medications may cause hypothyroidism, especially ones that treat psychiatric disorders. It’s important to talk to your doctor about all side effects of any potent medication regime you begin.

Doctor listening to baby's heartbeat.

Congenital disease

When babies are born with an underdeveloped thyroid or with no thyroid at all, they are born with an inherited form of hypothyroidism. Fortunately, most states now require newborn thyroid screening in order for parents to take the best next steps for their babies.

Pituitary gland on a brain.

Pituitary disorder

When the pituitary gland does not function properly and does not produce enough thyroid stimulating hormones, hypothyroidism can occur. This malfunctioning can be caused by a benign tumor in the pituitary gland.

Pregnant woman.


During or after pregnancy, a woman may develop hypothyroidism, often because they produce antibodies to their own thyroid gland. Left untreated, this could prove harmful to both mother and baby.

A bowl of Wakame seaweed salad.

Too much or too little iodine

Iodine is mostly found in seafood and seaweed and is crucial in the proper functioning of the thyroid. It’s important to regulate intake as too much iodine might also cause hypothyroidism. If you have any reason to suspect you might have hypothyroidism due to symptoms, do research, and consult a doctor.

Doctor listening to patient.

Post treatment of hyperthyroidism

Hyperthyroidism is a condition where the thyroid gland is overactive and produces too much thyroid hormones. This can result in sudden weight loss, irregular heartbeat, and nervousness. Sometimes by treating a hyperthyroid condition, hypothyroidism can occur.

Yumhee Park
Meet Our Writer
Yumhee Park

Yumhee Park is a former content producer for HealthCentral and helped bring important stories of health advocates to life as a member of the Live Bold, Live Now multimedia team.