Real or Not Real? An Elevated TSH

Area of Science:

• Endocrinology
• Clinical Chemistry

Background:

• Elevated thyroid-stimulating hormone (TSH) levels typically indicate hypothyroidism.
• Discordant thyroid function tests (normal free thyroxine and triiodothyronine with elevated TSH) warrant further investigation.

Purpose of the Study:

• To report a rare case of Macro-TSH.
• To highlight the importance of investigating incongruent thyroid function test results.

Main Methods:

• Case presentation of a 19-year-old male with fatigue and constipation.
• Laboratory evaluation including TSH, free thyroxine, and total triiodothyronine levels.
• Diagnostic confirmation using TSH antibody testing and gel filtration chromatography.

Main Results:

• The patient presented with a TSH level of 85 mIU/L, normal free thyroxine, and normal total triiodothyronine.
• Macro-TSH was diagnosed, confirmed by positive TSH antibody testing and gel filtration chromatography.
• This confirmed Macro-TSH as the cause of the elevated TSH.

Conclusions:

• Macro-TSH is a rare condition that can mimic hypothyroidism.
• Investigating TSH antibody levels or utilizing gel filtration chromatography is crucial when thyroid function tests do not align with clinical presentation.