Thyrotoxicosis

Toxic uninodular goitre

  • Toxic uninodular goitre 1
  • Toxic uninodular goitre 2
Image A: 99m Tc Thyroid scan with toxic nodule in right lobe and developing supression of left lobeImage A: 99m Tc Thyroid scan with toxic nodule in right lobe and developing supression of left lobe large image

 

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A toxic nodule may develop in either lobe of the thyroid in an otherwise normal gland. Initially the focal area of increased uptake will be seen with reduced uptake noted in the remaining thyroid. This is due to the negative feedback caused by a rising Thyroxine (T4) and/or T3 level and a falling TSH level.

 

Image A: 99m Tc Thyroid scan with toxic nodule in right lobe and developing supression of left lobe

 

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Image B: 99m Tc Thyroid scan with toxic nodule in right lobe and complete supression of left lobeImage B: 99m Tc Thyroid scan with toxic nodule in right lobe and complete supression of left lobe large image

 

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When the patient is biochemically thyrotooxic with an undetectable TSH level, the normal thyroid tissue will not be visualised.  This is the optimal time to treat the patient with 131I Iodine as the normal tissue will be spared a radiation dose.

 

Image B: 99m Tc Thyroid scan with toxic nodule in right lobe and complete supression of left lobe

 

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