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Thyroid autoimmunity, TSH lower in pregnant women of different African regions
Thyroid autoimmunity and thyroid-stimulating hormone levels tend to be lower in pregnant women with a sub-Saharan African background compared with North African background, according to published findings.
Kris Poppe, MD, PhD, of the department of endocrinology, University Hospital CHU Saint-Pierre in Brussels, and colleagues evaluated data on 1,683 pregnant women seen at the obstetric clinic of CHU Saint-Pierre from 2013 to 2014, to determine the prevalence of thyroid autoimmunity and subclinical hypothyroidism in women with different ethnic backgrounds. Subclinical hypothyroidism was defined using different first trimester TSH reference cutoffs of 2.5 mIU/L or greater from the Endocrine Society, 4 mIU/L or greater from the American Thyroid Association and 3.74 mIU/L or greater from the clinic.
Thyroid peroxidase antibodies, TSH and free thyroxine were measured and baseline characteristics recorded at the first antenatal visit. Ethnic backgrounds in the cohort included sub-Saharan African (28.6%), North African (44.8%) and white (26.6%, excluding women of Turkish, Hispanic and Middle East Asian ethnicities).
White participants had higher median TSH levels (1.5 mIU/L) compared with sub-Saharan African participants (1.3 mIU/L; P = .006) and North African participants (1.4 mIU/L; P = .014). The prevalence of thyroid autoimmunity was lower in sub-Saharan African participants (3.3%) compared with North African (8.6%) and white participants (11.6%; P < .001).
When the cutoff of 2.5 mIU/L was used, the prevalence of subclinical hypothyroidism was higher compared with the other reference cutoffs. The prevalence of subclinical hypothyroidism was higher in white participants compared with North African participants when the institutional (P = .013) or ATA cutoffs were used (P = .008).
“Pregnant women with a sub-Saharan African background have a significantly lower prevalence of thyroid autoimmunity and lower TSH levels as compared with women with North African or Caucasian backgrounds,” the researchers wrote. “However, ethnicity-specific reference ranges are not more specific, as compared with institutional reference values, for the diagnosis of subclinical hypothyroidism during the first trimester of pregnancy.” – by Amber Cox
Disclosure: Poppe reports various financial ties with IBSA Institut Biochimique SA and Merck.