Don't Miss Thyroid Disease in Kids

Laurie Scudder, DNP, NP; Andrew Bauer, MD

Disclosures

December 05, 2016

Editorial Collaboration

Medscape &

In This Article

Editor's Note:
A recent review[1] published in JAMA Pediatrics focused on thyroid disorders in children, emphasizing the common signs and symptoms that should alert primary care clinicians to consider a thyroid disorder. Medscape spoke with Andrew Bauer, MD, the senior author on this paper and director of the Pediatric Thyroid Center at The Children's Hospital of Philadelphia, about the key findings in the review.

Medscape: There has been some evidence of late of an increase in diagnosis of thyroid disorders in adults, especially nodules and low-grade carcinomas,[2] even though the US Preventive Services Task Force does not recommend routine screening.[3] On a big-picture level, is the incidence of thyroid disease in children changing?

Dr Bauer: Yes, but it depends on which form of thyroid disease we're talking about. And some of the increase is for different reasons, which range from differences in statistical methodology to environmental influences on actual disease rates.

There is an increased incidence of congenital hypothyroidism. Some of that has to do with changes in how we define a positive newborn screen. As the cutoff value for diagnosing congenital hypothyroidism on the basis of thyroid-stimulating hormone (TSH) screening has been lowered, the number of babies who will have a positive screen has increased.

As an example, if we identify babies with a TSH value of more than 10 mIU/L as positive, this avoids missing babies with real disease but will also introduce false-positive results owing to capture bias compared with a cutoff value of 40 mIU/L. With this general approach, the current estimated incidence has risen from 1 in 4000 approximately 15-20 years ago to 1 in 2000 now. But that increase is due to a statistical change, not a medical or physiologic reason.

I think the intention is good, but the reality is that more infants will need more formal testing and some may well end up on thyroid replacement therapy, typically for at least 3 years, before we figure out whether this is a lifelong requirement or not.

Medscape: Does screening, provided that the heel prick is obtained after 48 hours of life, catch all infants with congenital hypothyroidism?

Dr Bauer: The initial screen—when conducted, as you note, after 48 hours of life—is very good, especially with the lower cutoff values, for identifying a positive result. That is true particularly for full-term infants.

However, the pattern of normalization of TSH is much different for a premature infant. Some of that is because their endocrine system is also premature. Some of it is because many of them are sick when they're born, and they are therefore exposed to medicines that can lower the TSH value. It can be very tough to figure out which of those kids might benefit from thyroid hormone replacement, but most endocrinologists recommend initiating treatment only for premature infants with an elevated TSH.

Medscape: What about increases in the incidence of hypothyroidism in older kids—is that also a concern?

Dr Bauer: The issue of the increased incidence of autoimmune thyroid disease is a little bit more complicated because we don't track it very well. In contrast to congenital hypothyroidism, which is identified by newborn screening that is controlled by state registry disease databases in the United States as well as many countries worldwide, there are very few registries to report cases of autoimmune disease. We definitely see more of it, and in younger patients. When I was in training 15-20 years ago, I never saw 2-year-olds with autoimmune thyroid disease. Now I do.

 
When I was in training 15-20 years ago, I never saw 2-year-olds with autoimmune thyroid disease. Now I do.
 

There really has been a change. It's just hard to put a finger on it and determine an exact explanation. There is a genetic component (it clusters in families), and without question, environmental triggers are a concern.

Medscape: Are you specifically referring to endocrine disruptors? Is the use of these chemicals a factor?

Dr Bauer: That's definitely an important factor, although there are few data on endocrine disrupters associated with thyroid disease. As an example (but not an absolute explanation for autoimmune disease), bisphenol A (BPA) is an organic synthetic compound that was used in the manufacture of plastic storage containers and baby bottles. When these plastics are exposed to heat, for example in the microwave, the BPA leaches out of the plastic.

Animal models have shown that these chemicals can affect the endocrine system. Although we don't have great data in people, the animal models suggest that exposure to these substances may not only affect the exposed person, but also may lead to transgenerational changes in gene expression. Changes in the epigenetics of maternal DNA can be transmitted to the offspring. It's amazingly interesting and, I think, of great importance. From a preventive health perspective, it is important that we identify these products so that we can either reduce exposure or appropriately label products containing these disruptors, as we pursue and confirm more information on the potential impact on people.

The other endocrine disruptors to note are tea tree oil and lavender oil, which are commonly used in skin moisturizers and other products, as well as medications that leak into our watershed. All of these products appear to be linked to alterations in puberty. Again, similar to the previous discussion, it is important to emphasize that what we have right now is more association than causation data. However, although we don't know whether exposure is causal, exposure to some of these products is avoidable.

The last environmental exposure to briefly discuss is the importance of iodine. Most of our attention has been directed at eradicating iodine deficiency, because maternal iodine deficiency is the leading cause of severe congenital hypothyroidism and endemic goiter in children, adolescents, and adults and has a significant impact on quality of life and work capacity. The opposite situation, iodine excess, also exists in several countries worldwide—mostly in Asia, owing to dietary habits—and some evidence shows an increased risk for autoimmune thyroid disease in this context.

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