Hyperthyroidism, also known as “overactive thyroid”, is a condition where the thyroid gland
makes too much thyroid for what your body actually needs. This will alter the body’s organ
functions and generally push them to work too intensely (1).
What is the thyroid?
The thyroid is a small butterfly-shaped gland located in the front of the neck. It produces and
secretes thyroid hormones that can help control how your body uses energy. Since every part of
the body uses energy, thyroid hormone plays an important role in the function of almost every
organ, including the heart, brain, liver, kidneys, and skin (1,2).
What causes hyperthyroidism?
There are many causes of hyperthyroidism. Among them are:
Grave’s Disease. The most common cause of hyperthyroidism is Grave’s Disease. It is an
autoimmune disorder where the thyroid is attacked by your immune cells and is stimulated to
produce too much thyroid hormone (1,2).
Overactive thyroid nodules. Nodules are lumps in the thyroid that are generally benign and
not cancerous. However, if the nodules are overactive, as in the case of a single toxic nodule or
a toxic multinodular goiter, these can lead to too much thyroid hormone in the circulation (1).
Thyroiditis. The thyroid gland usually makes enough hormone to send out into the body, plus
enough to store. Thyroiditis is a condition where an infection can cause the thyroid gland to leak
out the thyroid hormone that it normally stores, raising thyroid hormone levels in the
Too much iodine. The thyroid gland needs iodine to make thyroid hormone. Having too much
iodine in the diet can cause or worsen hyperthyroidism in an already susceptible gland.
As outlined above, there are many different causes of hyperthyroidism, so be sure to check with
your physician to determine the cause.
What are some signs and symptoms of hyperthyroidism?
*These symptoms are a generalized group that have been noted in individuals with hyperthyroidism in the past, but
they overlap with many other diseases. If you have any combination of these symptoms, it does not always mean you
have hyperthyroidism. Rather, they are an indicator that it might be good to check thyroid function.
General/Metabolism-related factors (1,2)
· Nervousness or anxiety
· Weight loss
· Trouble sleeping
· Decreased tolerance to heat
· Enlarged thyroid gland
Gastrointestinal and Urinary Symptoms
· Frequent bowel movements
· Mild renal damage 3
· Rapid heart rate
· Irregular heartbeat
Do I have hyperthyroidism?
Since the symptoms of hyperthyroidism can potentially overlap with hypothyroidism, other
endocrine diseases, or even non-endocrine causes, the best way to know if you have
hyperthyroidism is to visit your primary care physician or an endocrinologist. By reviewing your
blood work and listening to your history, they can accurately diagnose and recommend a plan of
care or follow-up.
What blood work is needed to test for hyperthyroidism?
TSH (thyroid stimulating hormone)
TSH is a stimulating hormone released by the pituitary gland. It binds to your thyroid cells and
stimulates it to release thyroid hormone. If TSH levels are low, it could (in combination with a
high thyroid hormone level) indicate hyperthyroidism since high thyroid hormone levels will
cause the pituitary to release less TSH (2).
T4 and T3
T4 and T3 are your thyroid hormones. T4 is the one that is primarily checked, and if its levels
are abnormally raised*, it indicates hyperthyroidism (2).
*Important note- since the “normal” levels of T3 and T4 fall in a very wide range, individuals can have varying
definitions of what a “normal” or “abnormal” level is for them.
TSH Receptor Antibodies (2)
Thyroid stimulating immunoglobulin (TSI) is the specific TSH receptor antibody that sticks to
thyroid cell receptors and activates them, causing hyperthyroidism in Grave’s Disease. If there
are elevated levels of TSH receptor antibodies present in the bloodstream, specifically TSIs, this
turns on the thyroid and causes it to grow and secrete too much thyroid hormone.
Hyperthyroidism is treated differently in each individual, depending on the cause and severity.
Your primary care physician or endocrinologist will obtain your medical history, blood tests and
thyroid imaging to recommend a plan of care.
Among the potential plans of care are (1,2,4):
Thyroidectomy. Thyroidectomy is a surgery that can be partial (removing a part of the thyroid)
or total (removing the whole thyroid).
Antithyroid medication. Medications such as methimazole or propylthiouracil can be
administered to block the thyroid gland’s ability to make new hormones.
Radioactive iodine. Radioactive iodine can be administered orally as a small capsule. Since
the thyroid needs iodine to make more thyroid hormone, it takes up this oral iodine laced with
radioactivity, which then destroys the cells that take it up and prevents them from making more
3. Sönmez E, Bulur O, Ertugrul DT, Sahin K, Beyan E, Dal K. Hyperthyroidism influences renal function.
Endocrine. 2019 Jul;65(1):144-148. doi: 10.1007/s12020-019-01903-2. Epub 2019 Mar 23. PMID:
4. Reid JR, Wheeler SF. Hyperthyroidism: diagnosis and treatment. Am Fam Physician. 2005 Aug
15;72(4):623-30. PMID: 16127951.