Refining your approach to hypothyroidism treatment
Thyroid hormone supplementation can be complicated by a number of factors. These tips can help to ensure that you provide the best treatment possible.
PRACTICE RECOMMENDATIONS
› Prescribe levothyroxine 1.6 mcg/kg/d for healthy adult patients < 50 years of age with overt hypothyroidism. B
› Consider lower initial doses of levothyroxine in patients with cardiac disease (12.5-50 mcg/d) or subclinical hypothyroidism (25-75 mcg/d). B
› Titrate levothyroxine by 12.5 to 25 mcg/d at 6- to 8-week intervals based on thyroid-stimulating hormone measurements, comorbidities, and symptoms. C
› Closely monitor and provide thyroid supplementation to female patients who are pregnant or of reproductive age with concomitant hypothyroidism. C
Strength of recommendation (SOR)
A Good-quality patient-oriented evidence
B Inconsistent or limited-quality patient-oriented evidence
C Consensus, usual practice, opinion, disease-oriented evidence, case series
To maximize absorption, providers should review with patients the optimal way to take thyroid hormones. Levothyroxine is approximately 70% to 80% absorbed under ideal conditions, which means taking it in the morning at least 30 to 60 minutes before eating or 3 to 4 hours after the last meal of the day.3,9-13 Of note, TSH levels may increase slightly in patients taking proton pump inhibitors, but this does not usually require a dose increase of thyroid hormone.11 Given that some supplements, particularly iron and calcium, can interfere with absorption, it is recommended to maintain a 3- to 4-hour gap between taking those supplements and taking levothyroxine.12-14 For those patients unable or unwilling to adhere to these recommendations, an increase in levothyroxine dose may be required in order to compensate for the decreased absorption.
Don’t adjust hormone therapy based on clinical presentation alone. While clinical symptoms are important, it is not recommended to adjust hormone therapy based solely on clinical presentation. Common hypothyroid symptoms of dry skin, edema, weight gain, and fatigue may be caused by other medical conditions. While indices including Achilles reflex time and basal metabolic rate have shown some correlation to thyroid dysfunction, there has been limited evidence to show that longitudinal index changes reflect subtle changes in thyroid hormone levels.3
The most recent guidelines from the American Thyroid Association recommend that, “Symptoms should be followed, but considered in the context of serum thyrotropin values, relevant comorbidities, and other potential causes.”3
Special populations/circumstances to keep in mind
Malabsorption conditions. When a higher than expected weight-based dose of levothyroxine is required, physicians should review administration timing, adherence, and comorbid medical conditions that can affect absorption.
Several studies, for example, have demonstrated the impact of Helicobacter pylori gastritis on levothyroxine absorption and subsequent TSH levels.15-17 In one nonrandomized prospective study, patients with H pylori and hypothyroidism who were previously thought to be unresponsive to levothyroxine therapy had a decrease in average TSH level from 30.5 mIU/L to 4.2 mIU/L after H pylori was eradicated.15 Autoimmune atrophic gastritis and celiac disease, both of which are more common in those with other autoimmune diseases, are also associated with the need for higher than expected levothyroxine doses.17,18
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