Side Effects of Thyroid Medication

Learn about possible side effects of common thyroid replacement hormones.
Side Effects of Thyroid Medication

If you have a thyroid disorder, such as hypothyroidism, your doctor may recommend you take thyroid medication as part of your treatment plan. Taking thyroid medication can make a world of difference in your symptoms – especially where your energy, hair appearance, and weight are concerned.


Thyroid 101


The thyroid gland is a butterfly-shaped gland located at the base of your neck. It produces hormones that regulate your body’s energy use, along with many other important functions. As part of the endocrine system, the thyroid gland makes and stores hormones that help regulate the body’s metabolism in the form of blood pressure, blood temperature, and heart rate.


When your thyroid hormone production drops, your body processes slow down and change. Since your body needs a certain amount of these hormones to function properly, hypothyroidism can affect many different systems in your body.


Undiagnosed thyroid disease puts patients at risk for other ailments, such as cardiovascular diseases, osteoporosis and infertility.


What medications are out there?


Thyroid drugs, or synthetic forms of thyroid hormones, are often used to boost or regulate low thyroid levels in people with hypothyroidism.


Pure synthetic thyroxine (T4), taken once daily by mouth, fully replaces the thyroid gland and successfully treats the symptoms of hypothyroidism in most patients. Because the potency of generic thyroxine has varied considerably in the past, your physician may specify a brand name to treat your thyroid problem. The current branded forms of synthetic T4 are Synthroid®, Levoxyl®, Levothroid®, Tirosint® and Unithroid® For the few patients who do not feel completely normal taking a synthetic preparation of T4 alone, the addition of T3 (Cytomel®) may be of benefit.


If only there was one medication that worked for all of us — but the reality is that we each react differently to the different treatment options. Paloma Health works closely with our patients to investigate which treatment is ideal and what dosage is optimal.


It’s important to note that these medications are not a cure for hypothyroidism. They do not go after the condition itself, but rather the symptoms.


And what are the side effects of thyroid medication?


Most medications have at least one or two side effects, while many have a daunting list. We want to take some time to focus on some of the side effects of the three different drug treatment options for an underactive thyroid.


Note that many different brands manufacture the synthetic thyroid replacement hormones. We have listed the side effects of two of the most common medications. You should read the package insert that is given to you when you pick up your prescription to learn about the specific side effects associated with the medication you are taking.


Before diving into medication-specific side effects, please be aware of the risk of allergic reaction, specifically anaphylaxis. If you take any medication and notice a severe allergic response that includes any of the following, contact your doctor or get medical help immediately:


  • Difficulty breathing
  • Rash
  • Hives
  • Chest tightness
  • Swelling of the face, mouth, lips or tongue


Levothyroxine (or Synthroid)


This drug contains the synthetic form of one thyroid hormone, thyroxine (T4). Levothyroxine is the most commonly prescribed thyroid hormone replacement drug. T4 is the storage hormone and must be converted by the body into T3 to be used by cells.


Levothyroxine is the second most prescribed prescription medication in the United States, and the first most prescribed in the world. Many patients do very well on this medication when the right dosage is found by regular monitoring and adjusting.


Some of the most common side effects of levothyroxine include:


  • Weight loss
  • Headache
  • Tremor
  • Vomiting
  • Nausea
  • Stomach cramps
  • Diarrhea
  • Irritability
  • Insomnia
  • Nervousness
  • Excessive sweating
  • Fever
  • Increased appetite
  • Sensitivity to heat
  • Changes in menstrual cycle
  • Temporary hair loss – especially among adolescent patients during the first month of treatment


Contact your doctor if you notice any of the above side effects.


More serious side effects may also occur when taking levothyroxine. If you have rapid or irregular heartbeat or pulse, chest pain, or confusion/disorientation, discontinue use and get medical treatment immediately.


Levothyroxine interacts with some medications, meaning that some drugs (including some common over-the-counter meds, like aspirin) may cause changes in thyroid hormone levels and side effects. This affects the effectiveness and toxicity profiles of other medications. The extra five minutes you’ll spend at the pharmacy counter for the pharmacist consult will be well worth it so they can fully educate you about any interactions!


Paloma Health monitors everything (Free T4, Free T3, Reverse T3, and thyroid antibodies) and works closely with you to understand your symptoms and side effects.


Liothyronine (or Cytomel)


Our bodies need to convert the T4 in the above mentioned drugs to the active, usable thyroid hormone, triiodothyronine (T3). For many hypothyroid patients, our bodies don’t convert T4 to T3 as it should and we are left suffering symptoms.


Liothyronine contains the synthetic form of T3, which works at the cellular level to help with the delivery of oxygen and energy to cells, tissues, and glands throughout the body.


Liothyronine is typically used in combination with T4 medications to balance the ratio of the two main thyroid hormones present in our own bodies. It is not normally used alone because it is short-acting which can send your thyroid hormones on a bumpy ride.


Cytomel has a short list of mild side effects listed, which include:

  • Mild nausea
  • Temporary hair loss (more often in adolescents)


If the above side effects do not go away or they become severe, reach out to your practitioner.

Cytomel has been reported to be associated with some serious side effects. If you experience any of the following, let your doctor know immediately.


  • Rapid or irregular heartbeat
  • Rapid or irregular pulse
  • Chest pain or pounding in the chest
  • Sensitivity to heat
  • Leg cramps
  • Vomiting or diarrhea
  • Excessive sweating
  • Headache
  • Nervousness
  • Tremor
  • Changes in appetite
  • Weight changes
  • Changes in menstrual cycle


Thyroid hormone replacement drugs are powerful. This is why it is critical to be under careful medical supervision when on these drugs, especially when starting a new brand or increasing dosage level.


We believe that a slow, step-by-step method of reaching your optimal dose is easier on the body than the “sock it to me” approach that is so characteristic of our fast-paced culture.


Our bodies will not all react the same way to a specific medication or dosage. Finding the right thyroid treatment is tricky, and we are here to make the process as easy and efficient as possible.


Is Paloma Right For Me?

Hypothyroidism is a long-term commitment and we’re committed to you. Schedule a free, no-obligation phone consultation with one of our intake specialists to find out more.

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