Refining your approach to hypothyroidism treatment

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Applied Evidence

Refining your approach to hypothyroidism treatment

J Fam Pract. 2020 March;69(2):84-89

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References

1. Aoki Y, Belin RM, Clickner R, et al. Serum TSH and total T4 in the United States population and their association with participant characteristics: National Health and Nutrition Examination Survey (NHANES 1999-2002). Thyroid. 2007;17:1211-1223.

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3. Garber JR, Cobin RH, Gharib H, et al. Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. Endocr Pract. 2012;18:988-1028.

4. Jonklaas J, Bianco AC, Bauer AJ, et al. Guidelines for the treatment of hypothyroidism: prepared by the American Thyroid Association task force on thyroid hormone replacement. Thyroid. 2014;24:1670-1751.

5. Toft AD. Thyroxine therapy. N Engl J Med. 1994;331:174-180.

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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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