Thyroidology 1993 Aug;5(2):61-6
L-thyroxine overdose: a case of marked, severe, prolonged, excess ingestion and review of the literature.
Shapiro B, Gross MD, Geatti O.
Division of Nuclear Medicine, University of Michigan Medical Center, Ann Arbor 48109-0028.
A case of a man with thyroid cancer who ingested between 0.9 and 3.3 mg l-thyroxine per day for over 10 years (the highest dose for 3 years) is reported. This had been prescribed for suppression of TSH for a well differentiated thyroid cancer. He was essentially asymptomatic and suffered no apparent ill effects from this prolonged and markedly excessive dosage of l-thyroxine. The literature lists a wide range of ill effects from both chronic and acute thyroid hormone overdosage but also records many examples of tolerance to excessive levels of exogenous thyroid hormone. The various circumstances leading to thyroid hormone overdose and potential ill-effects are reviewed.