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Published on: July 19, 2019
Is the kidney a major storage site for thyroxine as thyroxine glucuronide?
Maarten Buitendijk1, Valerie Anne Galton
1Department of Physiology and Neurobiology, Dartmouth Medical School, Lebanon, New Hampshire 03756, USA.
Thyroid : Official Journal of the American Thyroid Association
|December 20, 2011
Summary
The kidney stores a significant amount of thyroxine (T4) as T4 glucuronide (T4G). This finding suggests the kidney plays a role in maintaining extrathyroidal serum T4 levels.
Area of Science:
- Endocrinology
- Renal Physiology
- Thyroid Hormone Metabolism
Background:
- Thyroxine (T4) is known to be stored as T4 glucuronide (T4G) in the kidney.
- Previous studies indicated higher radioactivity in kidneys than livers after T4 administration.
Purpose of the Study:
- To determine the relative amounts of conjugated and unconjugated T4 and T3 in kidney and liver.
- To verify if conjugated hormones are extractable and detectable by RIA.
Main Methods:
- Mice were injected with radiolabeled T4 or T3.
- Tissue extracts were analyzed by paper chromatography and RIA before and after beta-glucuronidase treatment.
Main Results:
- Over 95% of radioactivity in kidney and liver was extracted after T4 administration, primarily as T4G in the kidney.
- Endogenous T4 was substantially present as T4G in kidney and liver, undetectable by standard RIA.
- Kidney T4 content (T4+T4G) was significantly higher than in liver or serum, while kidney T3 content was low.
Conclusions:
- The kidney stores a significant amount of T4 as T4G.
- Rapid deconjugation of T4G in the kidney suggests its role in extrathyroidal serum T4 homeostasis.
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