A 43-year-old man presents for his thyroid checkup. He has known hypothyroidism secondary to Hashimoto thyroiditis, also known as chronic lymphocytic thyroiditis. He is taking levothyroxine (LT4) 250 μg (two 125-μg tablets once per day). Review of his prior lab results and notes (see Table 1) reveals frequent dose changes (about every three to six months) and a high dosage of LT4, considering his weight (185 lb).
Patients with little or no residual thyroid function require replacement doses of LT4 at approximately 1.6 μg/kg/d, based on lean body weight.1 Since the case patient weighs 84 kg, the expected LT4 dosage would be around 125 to 150 μg/d.
This patient requires a significantly higher dose than expected, and his thyroid levels are fluctuating. These facts should trigger further investigation.
Important historical questions I consider when patients have frequent or significant fluctuations in TSH include
• Are you consistent in taking your medication?
• How do you take your thyroid medication?
• Are you taking any iron supplements, vitamins with iron, or contraceptive pills containing iron?
• Has there been any change in your other medication regimen(s) or medical condition(s)?
• Did you change pharmacies, or did the shape or color of your pill change?
• Have you experienced significant weight changes?
• Do you have any gastrointestinal complaints (nausea/vomiting/diarrhea/bloating)?
MEDICATION ADHERENCE
It is well known but still puzzling to hear that, overall, patients’ medication adherence is merely 50%.2 It is very important that you verify whether your patient is taking his/her medication consistently. Rather than asking “Are you taking your medications?” (to which they are more likely to answer “yes”), I ask “How many pills do you miss in a given week or month?”
For those who have a hard time remembering to take their medication on a regular basis, I recommend setting up a routine: Keep the medication at their bedside and take it first thing upon awakening, or place it beside the toothpaste so they see it every time they brush their teeth in the morning. Another option is of course to set up an alarm as a reminder.
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