Levothyroxine is a widely prescribed medication used to treat thyroid conditions, primarily an underactive thyroid gland, a condition known as hypothyroidism. White blood cells, also called leukocytes, are a fundamental part of the body’s immune system. This article will examine whether taking levothyroxine can lead to a reduction in white blood cell count.
Understanding Levothyroxine and White Blood Cells
Levothyroxine is a synthetic hormone that mimics thyroxine (T4), a hormone naturally produced by the thyroid gland. It is prescribed to individuals whose thyroid gland does not produce enough of this hormone. Once ingested, levothyroxine is converted into triiodothyronine (T3), which is the active form of the thyroid hormone that helps regulate metabolism, growth, and development throughout the body.
White blood cells are a group of specialized cells that circulate in the bloodstream and tissues, forming a major component of the body’s immune defense system. Their primary role is to identify and combat foreign invaders such as bacteria, viruses, fungi, and parasites, thereby protecting the body from infection and illness. Different types of white blood cells, including neutrophils, lymphocytes, and monocytes, each play specific roles in this complex defense mechanism.
Levothyroxine and White Blood Cell Count
While levothyroxine is considered safe and effective for treating hypothyroidism, the direct association between levothyroxine itself and a low white blood cell count is rare. Low thyroid function has been linked to lower white blood cell counts, particularly neutrophils. In such cases, the low neutrophil counts often return to normal once thyroid hormone levels are normalized with treatment.
Levothyroxine should be distinguished from antithyroid medications, such as methimazole and propylthiouracil (PTU), which are used to treat an overactive thyroid (hyperthyroidism). These antithyroid drugs have a known, though rare, side effect called agranulocytosis, a severe decrease in neutrophils. Agranulocytosis increases the risk of severe infections. For methimazole, the risk of agranulocytosis increases with higher doses, while propylthiouracil does not show a dose-dependent effect.
Recognizing Low White Blood Cell Symptoms
A low white blood cell count might not always present with specific symptoms. The most common indicators arise from the body’s weakened ability to fight off infections. Individuals may experience frequent infections that are more severe or prolonged than usual.
Symptoms can include a high temperature, chills, and shivering. Other signs include a sore throat, mouth sores, or pain in the mouth. Fatigue, body aches, and flu-like symptoms are also common. Skin rashes, toothache, and difficulty healing from injuries or recovering from illnesses can also indicate a compromised immune system.
When to Seek Medical Advice
If you are taking levothyroxine and suspect you have a low white blood cell count or are experiencing related symptoms, contact your doctor promptly. This includes symptoms like a persistent fever, frequent infections, or unusual mouth sores. Do not discontinue your levothyroxine medication without consulting a healthcare professional, as stopping it abruptly can lead to worsening thyroid function.
Your doctor will order a complete blood count (CBC) to assess your white blood cell levels. If a low count is confirmed, they will investigate potential causes beyond your levothyroxine medication, as many factors can contribute to a low white blood cell count, including other medications, infections, or autoimmune conditions. Based on the findings, your doctor will determine the appropriate course of action, which may involve further tests, adjusting medication, or treating an underlying cause.