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Thyroid gland pigmentation and minocycline therapy
The American Journal of Pathology
|October 1, 1984
Summary
Minocycline treatment can cause black thyroid pigment, which is primarily lipofuscin similar to natural aging pigments. This thyroid discoloration associated with minocycline is generally considered harmless.
Area of Science:
- Endocrinology
- Histopathology
- Toxicology
Background:
- Minocycline, a tetracycline antibiotic, has been associated with thyroid gland discoloration.
- The nature of the pigment causing this black thyroid condition requires detailed characterization.
Purpose of the Study:
- To compare thyroid pigments in minocycline-treated patients with naturally occurring pigments.
- To investigate the composition and characteristics of minocycline-induced thyroid pigment.
Main Methods:
- Light and electron microscopy
- Histochemical staining (Schmorl, Ziehl-Neelsen, Sudan IV)
- Fluorescence microscopy
- Energy-dispersive x-ray analysis
Main Results:
- Pigments in black thyroids from minocycline-treated patients resembled human lipofuscins (fluorescent, Ziehl-Neelsen+, Sudan IV+).
- Minocycline-induced pigment in rats was nonfluorescent and Ziehl-Neelsen-, Sudan IV-.
- Pigments contained calcium, suggesting a possible link to minocycline or its metabolites.
Conclusions:
- Black thyroid in minocycline-treated patients is mainly lipofuscin, with a minor component of another pigment.
- Thyroid discoloration from minocycline appears to be an innocuous side effect with no observed functional changes.