Refining your approach to hypothyroidism treatment

Elderly patients are at higher risk for adverse effects of thyroid over-replacement, including atrial fibrillation and osteoporosis. While there have been no randomized trials examining target TSH levels in this population, a reasonable recommendation is a goal TSH level of 4 to 6 mIU/L for elderly patients ≥ 70 years.⁴

CASE

As a result of the patient’s elevated TSH level and symptoms of hypothyroidism, you start levothyroxine 150 mcg/d by mouth, counsel her on potential adverse effects, and schedule a follow-up visit with another TSH check in 6 weeks.

Follow-up laboratory studies 6 weeks later reveal a TSH level of 5.86 mIU/L (reference range, 0.45-4.5 mIU/L) and a free T4 level of 0.74 ng/dL (reference range, 0.8-2.8 ng/dL). Based on those results, you increase the dose of levothyroxine to 175 mcg/d.

Advancing age (> 70 years) and extreme obesity (BMI > 40) are independent risk factors for decreased levothyroxine absorption.

At her follow-up visit 12 weeks after initial presentation, her TSH level is 3.85 mIU/L. She reports feeling better overall with less fatigue, and she has lost 5 pounds since her last visit. You recommend she continue levothyroxine 175 mcg/d after reviewing medication compliance with the patient and ensuring she is indeed taking it in the morning, at least 30 minutes prior to eating. With improved but not resolved symptoms, she agrees to follow-up with repeat TSH laboratory studies in 6 weeks to determine whether further dose adjustments are necessary. Given that she is of reproductive age and her TSH level is suboptimal for pregnancy, you caution her about heightened pregnancy/fetal risks with a suboptimal TSH and recommend that she use reliable contraception.

CORRESPONDENCE
Christopher Bunt, MD, FAAFP, 5 Charleston Center Drive, Suite 263, MSC 192,Charleston, SC 29425; buntc@musc.edu