The following article has just been published. You might notice the importance of thyroxine testing (FT4) - not just TSH. And the mentions of causes other than "simple" inadequate thyroid, of the need for life-long monitoring, of increasing rates of hypothyroidism in infants.
Well worth reading if you have any interest at all.
Neonatal congenital hypothyroidism screening effective; questions remain for type, cutoff points
Endocrine Today, June 2016
Congenital hypothyroidism is one of the most common endocrine disorders present at birth, as well as the most common treatable cause of mental retardation.
Before neonatal screening became standard in the United States during the past 40 years, congenital hypothyroidism often went unrecognized in many children.
Samuel Refetoff, MD, warns that several less common conditions in which thyroid hormone deficiency is not implicated can give rise to congenital hypothyroidism. In these instances, the thyroid hormone level is normal or even high, and neonatal screening will not pick up the problem. Photo by David Christopher for the University of Chicago School of Medicine; printed with permission.
“[The babies] used to all be missed because the signs and symptoms appear maybe months later, and by that time, often, treatment is less effective,” Samuel Refetoff, MD, professor of medicine and pediatrics and director of the endocrinology laboratory at The University of Chicago Pritzker School of Medicine, told Endocrine Today. “If treatment is not given in the first 6 months of life, then the damage is going to be severe.”
According to 2014 guidelines from the European Society for Paediatric Endocrinology, “The harmonization of diagnosis, management and routine health surveillance would not only optimize patient outcomes, but should also facilitate epidemiological studies of the disorder.
“Individuals with [congenital hypothyroidism] require monitoring throughout their lives, particularly during early childhood and pregnancy,” according to the guidelines.
In a 2010 review published in the Orphanet Journal of Rare Diseases, researchers reported that the incidence of congenital hypothyroidism in the United States increased from one in 4,094 births in 1987 to one in 2,372 births in 2002.
According to the review, the incidence of preterm births has increased by nearly 20% during the past 20 years, which may be contributing to the overall increased incidence of congenital hypothyroidism. Another explanation may be a change in testing strategies.
“With increased sensitivity and accuracy of [thyroid-stimulating hormone] methods, many U.S. and other programs around the world have switched from a primary thyroxine follow-up TSH approach to a primary TSH test,” the researchers wrote. “If the TSH cutoff is lowered, more infants with milder congenital hypothyroidism will be detected.”
Endocrine Today interviewed several experts about the screening, infant characteristics and outcomes for congenital hypothyroidism.
Causes, types of congenital hypothyroidism
The most common underlying etiology of congenital hypothyroidism is thyroid dysgenesis, failure of the gland to develop or fully develop. According to Rosalind S. Brown, MD, CM, FRCP(C), senior associate physician in medicine and associate professor of pediatrics at Boston Children’s Hospital, thyroid dysgenesis accounts for 80% to 90% of cases.
“The thyroid gland starts its development in the fetus at the base of the tongue, and it has to migrate down to its normal location in the middle of the neck. If it does not migrate normally, it is referred to as an ectopic gland,” Stephen H. LaFranchi, MD, of the department of pediatrics, division of endocrinology at Oregon Health and Science University, told Endocrine Today. “All of those conditions — absent gland or hypoplasia or an ectopic gland — are grouped under thyroid dysgenesis, and that in a sense is a congenital malformation.”
The remaining 10% to 20% of cases are due to dyshormonogenesis, an abnormality in one of the steps necessary for thyroid hormone synthesis.
However, Refetoff said several less common conditions in which thyroid hormone deficiency is not implicated can give rise to congenital hypothyroidism.
In these instances, the thyroid hormone level is normal or even high, and neonatal screening will not pick up the problem, which can lead to severe symptoms later on. These are defects in the thyroid hormone cell transporter, metabolism and action at the receptor level.
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