Overview

Hypothyroidism is an underactive thyroid that makes too little thyroid hormone, and hyperthyroidism is an overactive thyroid that makes too much. The thyroid is a small, butterfly-shaped gland at the front of the neck. Its hormones control how fast the body uses energy, so an imbalance can affect weight, heart rate, mood, periods, and energy.

Thyroid problems are more common in women. Where diets contain enough iodine, the most common cause of an underactive thyroid is Hashimoto's thyroiditis, and the most common cause of an overactive thyroid is Graves' disease. Both are autoimmune conditions, in which the immune system targets the thyroid by mistake. Most people control thyroid conditions well with treatment and regular follow-up.

Symptoms

• Underactive: tiredness, feeling cold, weight gain, constipation, and dry skin
• Underactive: slow thinking, low mood, and heavy periods
• Overactive: weight loss with a normal appetite, fast heartbeat, and shaky hands
• Overactive: feeling hot, sweating, anxiety, and poor sleep
• Swelling at the front of the neck (goiter) in either condition
• Bulging, red, or gritty eyes in Graves' disease
• Seek urgent care for chest pain, a very fast or irregular heartbeat, fever with confusion, severe drowsiness, or trouble breathing or swallowing

Causes & Risk Factors

• Hashimoto's thyroiditis, the main cause of an underactive thyroid
• Graves' disease, the main cause of an overactive thyroid
• Thyroid nodules that make extra hormone
• Thyroid inflammation (thyroiditis), including after childbirth
• Past thyroid surgery, radioactive iodine, or radiation to the neck
• Certain medicines, such as amiodarone and lithium
• Female sex, family history, or another autoimmune condition such as type 1 diabetes

Complications

• Irregular heartbeat (atrial fibrillation) with an overactive thyroid
• High cholesterol with an underactive thyroid
• Bone thinning with a long-term overactive thyroid
• Fertility problems and pregnancy complications if left untreated
• Thyroid eye disease linked to Graves' disease
• Rare emergencies: thyroid storm (overactive) and myxedema coma (underactive)

Diagnosis

A blood test for TSH (thyroid-stimulating hormone) is usually the first step. A high TSH with a low free T4 points to an underactive thyroid, while a low TSH with a high free T4 or T3 points to an overactive thyroid. Antibody tests help confirm Hashimoto's (TPO antibodies) or Graves' disease (TSH receptor antibodies). A neck ultrasound or thyroid scan may be used to check the gland and any nodules.

Treatment

• Underactive: daily thyroid hormone replacement (levothyroxine), often lifelong
• Levothyroxine taken on an empty stomach, apart from iron and calcium supplements
• Regular TSH checks to adjust the dose, especially during pregnancy
• Overactive: antithyroid medicines such as methimazole or carbimazole
• Beta-blockers to ease a fast heartbeat and shaking while other treatment takes effect
• Radioactive iodine or surgery for some people, often followed by lifelong hormone replacement

Prevention

• Most autoimmune thyroid disease cannot be prevented, but early testing makes treatment easier
• Iodized salt in normal amounts, and no high-dose iodine or kelp supplements without advice
• Telling a doctor about any family history of thyroid disease
• Thyroid testing before or early in pregnancy when there are symptoms or risk factors
• Seeing a doctor for symptoms rather than self-treating with supplements

The Internal Medicine and Laboratory departments at AlHayat Medical Center diagnose and follow up underactive and overactive thyroid conditions.

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