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Macro TSH in patients with subclinical hypothyroidism
Naoki Hattori1, Takashi Ishihara2, Keiko Yamagami3
1Department of Pharmaceutical Sciences, Ritsumeikan University, Shiga, Japan.
Clinical Endocrinology
|November 13, 2014
Summary
Macro TSH, a cause of elevated thyroid-stimulating hormone (TSH) in subclinical hypothyroidism, was found in 1.62% of patients. This macro TSH, often due to TSH autoantibodies, shows low bioactivity, potentially negating the need for thyroid hormone replacement.
Area of Science:
- Endocrinology
- Clinical Chemistry
Background:
- Thyroid-stimulating hormone (TSH) is a key indicator of thyroid function.
- Subclinical hypothyroidism presents with elevated TSH despite normal thyroid hormone levels.
- Macro TSH is a recognized cause of elevated TSH in these patients.
Purpose of the Study:
- To determine the prevalence of macro TSH in subclinical hypothyroidism.
- To characterize the nature and bioactivity of macro TSH.
Main Methods:
- A 2-year cross-sectional observational study included 681 patients with subclinical hypothyroidism.
- Polyethylene glycol (PEG) precipitation screened for macro TSH.
- Gel filtration chromatography and bioassays analyzed macro TSH characteristics.
Main Results:
- Macro TSH was identified in 1.62% (11/681) of patients with subclinical hypothyroidism.
- The identified macro TSH was heterogeneous, including TSH-bound autoantibodies (IgG, non-IgG) and human anti-mouse antibodies (HAMA).
- Macro TSH demonstrated significantly reduced bioactivity.
Conclusions:
- Macro TSH is a heterogeneous entity, frequently involving TSH and anti-TSH autoantibodies.
- High PEG-precipitable TSH (>90%) with TSH >10 mU/L warrants investigation for macro TSH.
- Low bioactivity of macro TSH suggests thyroid hormone replacement may not be necessary for subclinical hypothyroidism, except in cases with high free TSH.
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