What are the causes of low free T4 levels?
Free T4 refers to serum free thyroxine. Low serum free thyroxine may be caused by subacute thyroiditis, hypoproteinemia, pituitary lesions, and other conditions.
After being infected with viruses such as Coxsackie virus, influenza virus, and mumps virus, patients with subacute thyroiditis may develop the condition. Due to inflammatory stimulation, thyroid function may temporarily decline, resulting in low serum free thyroxine. This disease is self-limiting, and most patients can self-recover. Those without clinical symptoms can be followed up and observed without worry.
Patients with hypoproteinemia due to inadequate protein intake or malabsorption may experience reduced thyroid nutrition due to decreased protein levels in the body, leading to hypothyroidism and low serum free thyroxine. Timely medical attention usually leads to a good prognosis for these patients. However, if treatment is not timely, complications such as infection and coagulation disorders may occur.
If a patient has a pituitary lesion, it can affect the production of thyroid-stimulating hormone, leading to low serum free thyroxine. Patients should visit the hospital as soon as possible to identify the cause, actively seek treatment, improve prognosis, and avoid permanent hormone deficiency.
In addition to the above reasons, low serum free thyroxine may also be caused by congenital thyroid deficiency, thyroid cancer, and other reasons.
