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Overt thyroid dysfunction rare in cystic fibrosis
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Patients with cystic fibrosis rarely have overt thyroid dysfunction despite a number of them having abnormal serum thyroid function tests, according to study findings published in Thyroid.
“In this study of [cystic fibrosis] patients with varying disease severity ... no subjects had recent excess iodine exposure, and significant overt thyroid dysfunction was not observed,” the researchers wrote.
Sun Y. Lee, MD, of the section of endocrinology, diabetes and nutrition at Boston University Medical Center, and colleagues evaluated 89 adults (54% men; mean age, 24.4 years) with cystic fibrosis seen at the Emory CF Center between Jan. 1, 2011, and Dec. 31, 2014, to determine the prevalence of thyroid dysfunction among them. A comparison was also made between hospitalized (n = 35) and ambulatory (n = 54) patients.
Banked specimens from an inpatient clinical trial were used to obtain sera from hospitalized participants. Medical records were used to assess demographics, forced expiratory volume in 1 second (FEV1) and medication use. Associations between covariates and thyrotropin, free thyroxine and thyroid dysfunction risk were assessed by multivariate regression models. Mean FEV1 was 63%.
There were no statistically significant differences between hospitalized and ambulatory participants for median thyrotropin or free T4, for frequency of abnormal thyrotropin or free T4, or for positive thyroid peroxidase (TPO) antibodies.
Abnormal serum thyroid function tests were found in 24 participants, and these included slightly low free T4 levels with normal thyrotropin levels (n = 17), slightly elevated thyrotropin with normal free T4 levels (n = 2), slightly elevated thyrotropin with low free T4 levels (n = 1), isolated mildly elevated thyrotropin (n = 2), mildly suppressed thyrotropin and normal free T4 levels (n = 1), and lower serum thyrotropin with slightly low free T4 levels (n = 1).
A decrease in FEV1 with increasing age (P = .041) was suggested by a weak negative association between age and FEV1.
“Overt thyroid dysfunction was rare in this cohort of 89 patients with [cystic fibrosis],” the researchers wrote. “Although 24 (27%) of patients had abnormal serum thyroid function tests with 19 (34%) of the measured serum [free] T4 levels being abnormal, the vast majority of those abnormal tests were mild. With iodine-containing expectorant no longer in routine use, mild thyroid dysfunction seen in this cohort is likely related to non-thyroidal illness, rather than intrinsic thyroid dysfunction.” – by Amber Cox
Disclosure: The researchers report no relevant financial disclosures.
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