Help with Thyroid Level Question

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Ok I'm confused about thyroid levels in hypo/hyperthyroidism. Had a question: The patient has an elevated serum thyroxine level. This indicates which disease process?

Answer is hypothryroidism.

Review books and interent say that there will be decreased T4 though in hypothyroidism? Can anyone help explan this to me?

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Specializes in Psych/Mental Health.

Doesn't make sense. Are you sure it's not elevated TSH?

High T4 should be hyperthyroidism.

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Specializes in Adult Nurse Practitioner.

T4 is the prohormone excreted from the thyroid when stimulated by TSH. TSH is stimulated through a feedback mechanism when free T3 is low. Conversely, when free T3 levels are high, the stimulation will be "turned off" so to speak and TSH levels will decrease. When you have elevated T4, free T3 and decreased TSH...you have a hyperthyroid state. When TSH is increased, T4 and free T3 are decreased...you have a hypothyroid state. This is why thyroid medication is moved up and down according to TSH levels: if TSH levels are above normal, you raise the dosage and conversely, if TSH is below normal, you lower the dosage even if there has been some improvement.

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Specializes in Pedi.
T4 is the prohormone excreted from the thyroid when stimulated by TSH. TSH is stimulated through a feedback mechanism when free T3 is low. Conversely, when free T3 levels are high, the stimulation will be "turned off" so to speak and TSH levels will decrease. When you have elevated T4, free T3 and decreased TSH...you have a hyperthyroid state. When TSH is increased, T4 and free T3 are decreased...you have a hypothyroid state. This is why thyroid medication is moved up and down according to TSH levels: if TSH levels are above normal, you raise the dosage and conversely, if TSH is below normal, you lower the dosage even if there has been some improvement.

In primary hypothyroidism. TSH is a useless measure in someone being treated for central hypothyroidism, because their brain isn't producing it in the first place. My Endocrinologist shakes his head any time another doctor of mine checks a TSH without also checking T4 and free T4 levels.

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