What Are the Effects of High Thyroxine Levels?

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  • Written By: wiseGEEK Writer
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  • Last Modified Date: 12 October 2019
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Having high thyroxine levels, or an elevation in T4, principally induces a state of hyperthyroidism. This may cause a variety of symptoms, including weight loss, hair loss, insomnia, and trembling. It is also associated with fatigue, poor tolerance of higher temperatures, and perspiration. People with hyperthyroidism may notice other symptoms like anxiety, palpitations, and a growth at the base of the neck called a goiter. Generally, the presence of hyperthyroidism can be explained by Graves' disease, taking too much T4 to treat low thyroid levels, growths on the thyroid gland or some temporary conditions like a virus, and these causes help to indicate treatment.

The purpose of the thyroxine is to regulate the body’s metabolic system, use calories, and stimulate, as needed, certain neurotransmitters like norepinephrine. Essentially, in the presence of high levels of thyroxine, thyroid hormones signal these systems to overwork and to produce more than is needed. The body begins to consume calories too quickly and produces an excessive amount of neurotransmitters. Thus, the principal symptoms of too much thyroxine are agitation, weight loss, shakiness, and poor sleep.


Individuals with high thyroxine levels also have excessive perspiration and difficulty tolerating heat because the hormone helps regulate temperature. Patients feel fatigued because their bodies are like engines that are running at too high a speed. Unfortunately, even with fatigue, some people have difficulty sleeping, and they may not be able to get adequate rest at night. Though weight loss is a common symptom, some people also have weight gain, because the body is demanding a much a higher calorie level than is ordinary, translating to overeating.

Other symptoms associated with high levels of thyroxine progressively worsen if the condition does not receive treatment. The heart may experience significant stress, which risks the possibility of dangerous arrythmias, congestive heart failure, and angina. These symptoms might occur with others like shortness of breath, palpitations, or chest pain. Elevated thyroxine also can lead to fragile bones and ultimately to osteoporosis.

Fortunately, high thyroxine levels are usually well recognized, and hyperthyroidism may be confirmed with a few laboratory tests. Doctors then must determine the cause to direct the choice of treatment. For some people, high thyroxine levels are due to the development of a disorder called Graves' disease, which creates excess T4. Other causes include viruses, and treatment for hypothyroidism where the patient is taking too high a dose of thyroxine.

Depending on the cause of high thyroxine levels, treatment might include medications to temporarily reduce T4. People with hypothyroidism need tests to evaluate their thyroxine levels and will require adjustment to their medication dose. Sometimes it is necessary to take more permanent steps and remove all or part of the thyroid gland. If the whole gland most be removed, patients would then require supplementary T4, since having too little thyroxine is just as dangerous as having too much.


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Post 3

I had high thyroxine t4 levels for a while when I was being treated for hypothyroidism. That's actually how my doctor knew that my thyroid had started producing more hormones. I basically went from symptoms of hypothyroidism like fatigue and weight gain to symptoms of hyperthyroidism. I lost several pounds, my blood sugar was lower than usual and I felt very energetic.

Post 2

@SarahGen-- One of the results could be wrong. Unless you have started taking medication during this time to treat hyperthyroidism levels, your thyroid hormone production won't change so quickly.

Something else to think about is reference numbers. Each laboratory has different reference points for diagnosis. So one lab might tell you that you have normal thyroid levels whereas another might say the results are abnormal.

Most doctors will not diagnose simply based on lab results. They will also look at symptoms. Do you have symptoms of high thyroxine levels? Are you losing weight, do you have heart palpitations, do you have hair loss? If you have these symptoms, tell your doctor right away.

Post 1

I was diagnosed with hyperthyroidism due to high T4 levels last month. This month, I got another blood test at a different hospital and I was told that I have normal thyroxine levels. How is this possible?

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