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Am Fam Physician. 2022;105(1):7-8

Original Article: Hypothyroidism: Diagnosis and Treatment

Issue Date: May 15, 2021

See additional reader comments at:

To the Editor: The article by Dr. Wilson and colleagues included many useful evidence-based pearls. However, the authors' assertion that endocrinology referral is routinely indicated for pregnant persons with preexisting hypothyroidism is not supported by their cited references.

The authors state that “The lower and upper limits of normal TSH [thyroid-stimulating hormone] drift downward during pregnancy, which, with geographic and ethnic variation, supports the recommendation to include endocrinology referral in managing pregnant patients with hypothyroidism.” The guideline cited for this sentence does not include language about endocrinology referral.1 One reference for Figure 2 and Table 9 in the article includes a mention of specialty; that reference is to a previous American Family Physician article on hypothyroidism,2 which referenced a 2004 study that concluded: “the prevention of hypothyroidism and its possible adverse effects on the fetus and pregnancy…requires the combined efforts of primary care physicians, endocrinologists, obstetricians, and the women themselves.”3 A 2017 guideline, by the same lead author, is cited in the current article and includes no mention of specialty.4

Beneficial patient-oriented outcomes result from appropriate TSH monitoring and levothyroxine dosing, not from the specialty of the clinicians performing those tasks. Family physicians can adjust levothyroxine dosing during pregnancy, even if doing so optimally includes identifying “population-based trimester-specific reference ranges for serum TSH…through assessment of local population data.”4 The American College of Obstetricians and Gynecologists 2020 guideline on thyroid disease in pregnancy recommends maintaining the TSH between “the lower limit of the reference range and 2.5 milliunits/L,” and does not mention a need for routine endocrinology referral.5

The evidence base does not support the routine referral of pregnant persons with preexisting hypothyroidism to an endocrinologist. It is fully within a family physician's scope of practice to independently treat most pregnant patients with hypothyroidism.

Editor's Note: Dr. Middleton is an assistant medical editor for AFP.

In Reply: We are grateful for Dr. Middleton's letter stating the reasons why family physicians could and should feel comfortable treating pregnant patients with hypothyroidism.

Having independently treated pregnant patients with preexisting hypothyroidism, we think this type of patient care in otherwise low-risk patients is within the scope of family physician practice, and we did not intend to construe referral as a mandate. For example, less experienced or comfortable family physicians may refer a couple or few patients, then feel comfortable assuming full care responsibilities after that. However, we are aware of the reduction in the number of family physicians delivering babies1 and did not want to further dissuade readers who may be more comfortable comanaging hypothyroidism in prenatal patients with our endocrinology colleagues.

We hope the clarifications made to the article online reflect the data and our clinical reasoning while remaining aware and respectful of the wide range of practice, skills, and comfort of our family physician colleagues.

Email letter submissions to Letters should be fewer than 400 words and limited to six references, one table or figure, and three authors. Letters submitted for publication in AFP must not be submitted to any other publication. Letters may be edited to meet style and space requirements.

This series is coordinated by Kenny Lin, MD, MPH, deputy editor.

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