Thyrotoxicosis factitia explained

Thyrotoxicosis factitia
Field:	Endocrinology

Thyrotoxicosis factitia (alimentary thyrotoxicosis, exogenous thyrotoxicosis)^{[1] [2]} is a condition of thyrotoxicosis caused by the ingestion^[3] of exogenous thyroid hormone.^{[4] [5]} It can be the result of mistaken ingestion of excess drugs, such as levothyroxine^[6] and triiodothyronine,^[7] or as a symptom of Munchausen syndrome. It is an uncommon form of hyperthyroidism.

Patients present with hyperthyroidism and may be mistaken for Graves’ disease, if TSH receptor positive, or thyroiditis because of absent uptake on a thyroid radionuclide uptake scan due to suppression of thyroid function by exogenous thyroid hormones.^[8] Ingestion of thyroid hormone also suppresses thyroglobulin levels helping to differentiate thyrotoxicosis factitia from other causes of hyperthyroidism, in which serum thyroglobulin is elevated. Caution, however, should be exercised in interpreting thyroglobulin results without thyroglobulin antibodies, since thyroglobulin antibodies commonly interfere in thyroglobulin immunoassays causing false positive and negative results which may lead to clinical misdirection. In such cases, increased fecal thyroxine levels in thyrotoxicosis factitia may help differentiate it from other causes of hyperthyroidism.

See also

• Foodborne illness
• Liothyronine

Notes and References

1. Mathioudakis N., Cooper D.S. (2015) Exogenous Thyrotoxicosis. In: Davies T. (eds) A Case-Based Guide to Clinical Endocrinology. Springer, New York, NY
2. Lucie Wartique, Lucie Pothen, Nathalie Pirson, Michel P. Hermans, Michel Lambert & Halil Yildiz (2017) An unusual cause of epidemic thyrotoxicosis. In: Acta Clinica Belgica, 72:6, 451–453, DOI: 10.1080/17843286.2017.1309336
3. Web site: Hamburger Thyrotoxicosis. www.vivo.colostate.edu.
4. 10.1136/bmj.g5128 . 25146390 . 1476727 . Diagnosis and management of thyrotoxicosis . BMJ . 349 . g5128 . 2014 . Vaidya . B . Pearce . S. H. S .
5. Pearce EN: Diagnosis and management of thyrotoxicosis. In: BMJ. 2006 Jun 10; 332(7554): 1369–1373.
6. Geraldo Medeiros-Neto: Thyroxine Poisoning. in: Endotext, Created: July 17, 2018.
7. Kang GY et al.: Thyroxine and triiodothyronine content in commercially available thyroid health supplements. In: Thyroid. 2013 Oct; 23(10): 1233-1237.
8. 10.1258/acb.2007.007163 . 18482926 . Thyrotoxicosis factitia masquerading as recurrent Graves' disease: Endogenous antibody immunoassay interference, a pitfall for the unwary . Annals of Clinical Biochemistry . 45 . 3 . 325–327 . 2008 . Jahagirdar . V R . Strouhal . P . Holder . G . Gama . R . Singh . B M . 34751194 . free .