USMLE Internal Medicine Review 11 12 Diagnostic findings for Hyperthyroidism and Thyrotoxicosis

USMLE Internal Medicine Review 11 12 Diagnostic findings for Hyperthyroidism and Thyrotoxicosis

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Let’s start our USMLE Review with Hypothyroidism and Hyperthyroidism from the Gold Standard USMLE Foundations of Medicine Audio Review program.

 

Play USMLE Audio MP3 11 12 Hyperthyroidism and Thyrotoxicosis Below

 

Begin 11 12 Hyperthyroidism and Thyrotoxicosis Transcription

Moving now to lab findings in hyperthyroidism and thyrotoxicosis. Essentially the combination of which elevated serum level with which suppressed level provides the diagnosis of hyperthyroidism? The combination of an elevated FT4 (free Thyroxine) with a suppressed TSH provides a diagnosis of hyperthyroidism.

If eye signs are present along with the hyperthyroidism what is almost surely the diagnosis?

  • If eye signs are present diagnosis of Graves’ disease can be made without further testing.

And if eye signs are absent and the patient is hyperthyroid with or without goiter, which diagnostic test should be performed?

  • Radionuclide uptake test should be performed.

An elevated uptake is diagnostic of which two conditions?

  • An elevated radionuclide uptake result is diagnostic of Graves’ disease or toxic nodular goiter.

While a low uptake is often seen in patients with a spontaneously resolving hyperthyroidism such as occurs in which two etiologies? Just list them please.

  • A low radionuclide uptake is often seen in patients with resolving Subacute Thyroiditis or a flare up of Hashimoto’s thyroiditis.

If both free Thyroxine and TSH are elevated, which two etiologies of hyperthyroidism need be considered?

  • If both free Thyroxine and TSH are elevated, a TSH-secreting pituitary tumor or pituitary resistance syndrome should be considered.

And if free Thyroxine is normal and TSH is suppressed, which other level should be checked?

  • FT3, free tri-iodothyronine should be checked.

An elevated FT3 reveals either of which two etiologies?

  • An elevated FT3 level in the context of normal free Thyroxine and suppressed TSH in the hyperthyroid patient suggest either early Graves’ disease or T3-secreting toxic nodules.  And a low FT3 reading in the same context will be found in either of two settings.

First, which thyroid syndrome involving abnormalities in thyroid related hormones and function tests and occurring in patients with severe systemic disease?

  • Low FT3 may reveal sick euthyroid syndrome.

Or second, low FT3 could mean the patient is taking either of which two types of agents?

  • Corticoids or dopamine.

Thyroid auto-antibodies, TG and TPO are normally present in both Graves’ disease and Hashimoto’s thyroiditis.

Which other auto-antibody is specific for Graves’ disease alone?

  • TSH-R antibody.

TSH-R antibody can be a useful diagnostic test in two patient settings. First, in the hyperthyroid patient with what type of emotional presentation? The so-called apathetic hyperthyroid patient.

And second the patient without obvious signs and lab findings of Graves’ disease who presents with which unilateral symptom?

  • Unilateral exophthalmus or proptosis.

Student doctor please pause the tape and summarize or comment on diagnostic lab findings in hyperthyroid patients. Please include FT4, TSH, radionuclide uptake, FT3, and auto-antibody testing.

  • A combination of an elevated FT4 and a suppressed TSH makes a diagnosis of hyperthyroidism.  If eye signs are also present, Graves’s disease is indicated without the need for further testing. If eye signs are absent and the patient is hyperthyroid with or without goiter, radionuclide uptake test should be performed. An elevated uptake is diagnostic of Graves’ disease or toxic nodular goiter. Low uptake is seen in patients with spontaneously resolving hyperthyroidism as with Subacute Thyroiditis or a flare up of Hashimoto’s thyroiditis. If both FT4 and TSH are elevated, TSH -secreting pituitary tumor or pituitary resistance syndrome should be considered. If FT4 is normal and TSH is suppressed, FT3 should be checked. FT3 is elevated in early Graves’ disease or in T3-secreting toxic nodules. Low FT3 will be seen in sick euthyroid syndrome and in patients taking corticoids or dopamine. Thyroid auto-antibodies, TG and TPO are normally present in both Graves’ disease and Hashimoto’s Thyroiditis, while TSH-R antibody is specific for Graves’ disease alone. TSH-R antibody can be a useful diagnostic test for the so-called apathetic hyperthyroid patient or for the patient without obvious signs or lab findings of Graves’ disease who presents with unilateral exophthalmus or proptosis.

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