(1) usually intentional ingestion by a person with a psychiatric disorder. The patient may be in a medically-related field with access to thyroid preparations. When questioned on ingestion of thyroid hormone usually will adamantly deny.
(2) occasionally accidental (Feit and Feit describe a woman who was accidentally taking her pet dog's replacement thyroid preparation)
(3) occasionally as an unreported additive to a weight loss preparation
Clinical findings:
(1) There are clinical signs of thyrotoxicosis, depending on hormone exposure, except that ophthalmopathy is absent.
(2) The thyroid gland is usually not enlarged. It may be atrophic with chronic ingestion.
(3) Radioactive iodine uptake is abnormally low, but this can be increased if TSH is administered
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Laboratory Test
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Findings
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thyroxine
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elevated (may be low or normal if T3 elevated)
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tri-iodothyronine (T3)
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elevated (may be normal if thyroxine elevated. If pure thyroxine is being used, then T3 would be low.)
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serum TSH
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undetectable to very low
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serum thyroglobulin
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very low, may be at lower limit of normal reference range
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serum antithyroid and thyroid microsomal antibodies
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absent (presence may indicate chronic thyroiditis. The presence of antibodies may explain low serum values of thyroglobulin.)
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where:
• If the person is only episodically taking the hormone, then the serum TSH and thyroid gland size may be normal.
Theoretically this needs to be distinguished from the extremely rare malignant tumor producing thyroid hormone without thyroglobulin.
