Self-Medicating With Synthroid

Bruce M. Gardner, MD

Disclosures

March 13, 2003

Question

I have a patient who is taking Synthroid (levothyroxine sodium; Abbott Laboratories, North Chicago, Illinois) and who periodically increases her own dosage due to fatigue. However, her thyroid-stimulating hormone (TSH) level is always normal when checked, even with the intermittently increased medication. Can individuals actually suppress their own thyroid and thus have a normal TSH when tested?

Response from Bruce M. Gardner, MD

Your question is fundamentally one of compliance...your patient taking medication the way she wants, when she wants. Any patient could possibly self-regulate medication and succeed in reaching targets, against better medical judgment. It is estimated that 21% to 55% of patients are noncompliant (now less judgmentally known as "nonadherent") with their prescriptions.[1]

Hypothyroidism is common: 2% of women and 0.5% of men in the United States have clinical evidence of the condition. After age 60, the incidences increase to 6% and 2.5%, respectively.[2]

TSH levels are used to monitor treatment; yet interestingly, the TSH will show abnormalities often several years before the L-thyroxine (T4) level decreases (subclinical hypothyroidism). If the TSH is greater than 10 microIU/L progression to overt hypothyroidism is likely.[3] Treatment of subclinical hypothyroidism is controversial, however, early treatment may help correct commonly associated lipid abnormalities.[3,4,5] Unfortunately, early treatment can accelerate bone loss in elderly women.[5]

Your patient, although acting against common medical practice, manages to keep herself healthy through self-administration of her thyroid hormone. I would never condone such practices, as serious consequences of over- or undermedication can occur. Nevertheless, her persistently favorable TSH could be due to the long half-life of T4 which is approximately 6-7 days in normal subjects.[6]

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