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Endocrine Care: Aidan McElduff, Patrick McElduff, Veronica Wiley, and Bridget Wilcken Neonatal Thyrotropin as Measured in a Congenital Hypothyroidism Screening Program: Influence of the Mode of Delivery J Clin Endocrinol Metab 2005; 90: 6361-6363 [Abstract] [Full text] [PDF]

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Re: Do babies born by caesarean delivery have higher postnatal TSH?

Aidan McElduff, Patrick McElduff, Veronica Wiley, and Bridget Wilcken   (4 January 2006)

Do babies born by caesarean delivery have higher postnatal TSH?

Serap Turan, Abdullah Bereket   (21 December 2005)

Re: Do babies born by caesarean delivery have higher postnatal TSH? 4 January 2006
Aidan McElduff, Endocrinologist Royal North Shore Hospital, Sydney, Australia, Patrick McElduff, Veronica Wiley, and Bridget Wilcken Send letter to journal: Re: Re: Do babies born by caesarean delivery have higher postnatal TSH? aidanm{at}med.usyd.edu.au Aidan McElduff, et al.	We have read with interest the letter of Turan and Bereket and their abstract (their reference 2). They report results that are different from ours in a similar study. The TSH levels that they report in their letter do not have units. If these are mIU/L, then they are very different from our results, perhaps indicating some difference in methodology, in population iodine status, or some other factor. Understanding this difference is important if neonatal TSH levels are ever to be of use in following population iodine status. First, we believe that they have misinterpreted our paper. They highlight prematurity as the likely cause for the elevated TSH levels that we found on day 3 following caesarean section. We believe this to be incorrect. We analyzed a subset of over 1800 babies born after 37 weeks of gestation (term) and adjusted for gestational age. Of course, there is always the potential for residual confounding, but we think this is unlikely. The hypothesis tested in our paper was that the topical iodine used in preparation for caesarean section contributed to the difference in TSH levels. Turan et al commented that iodine status of the babies was not studied directly, which is correct. We would like to know how their women were prepared for caesarean section. Was topical iodine used? This, in itself, may explain the different findings although the marked difference in actual TSH value between the 2 studies suggests other unidentified confounders. It would also be of interest to know the distribution of the TSH levels in Turan’s subgroups. TSH values are not normally distributed. The mean ± SD can hide subtle differences. Our data suggests that TSH levels begin to stabilize on the second day. We are puzzled by Turan’s finding of higher T4 levels on day 3 in the presence of the same TSH level. This is not easily understood from the physiological point of view. Finally, we actually agree with their conclusion. Care should be taken in extrapolating our results to other centers. We believe our data accurately describes our population, but each area will need to make their own assessment because other important factors influence neonatal TSH measurement, as we stated in our paper.
Do babies born by caesarean delivery have higher postnatal TSH? 21 December 2005
Serap Turan, Pediatric Endocrinology Marmara University, Abdullah Bereket Send letter to journal: Re: Do babies born by caesarean delivery have higher postnatal TSH? serapdemircioglu{at}yahoo.com Serap Turan, et al.	We read with great interest the paper by McElduff et al (1). The authors report the influence of the mode of delivery on neonatal TSH as measured in congenital thyroid screening. They found that, the mean TSH value was higher in the caesarean section group, and also that babies delivered by cesarean section are more likely to have TSH level higher than 5 mIU/L on day 3. In a similar study, we have recently investigated the influence of the mode of delivery on postnatal thyroid functions in 843 babies. Our results do not support the results of Mc Elduff et al. We have found that serum T4, TSH and f-T4 levels tended to be higher in vaginally delivered group compared to elective caesarean section group during the first week of life. However, the only statistically significant difference was the higher T4 levels at 3rd day in vaginal delivery group (15.2±2.9 µg/dL vs.12.5±2.7 µg/dL, p < 0.05) (2). Since, iodine status of the babies was not studied directly in either our and McElduff’s study, it is difficult to explain the differences in thyroid function tests in vaginally or cesarean section delivered babies based on iodine status. Several other factors might be responsible for these differences. First of all, as they pointed out, babies delivered by caesarean section were more likely to have been delivered earlier than babies delivered by vaginal delivery (P < 0.001). 10.8% of the babies delivered by caesarean section were born before 37 weeks, whereas this ratio was 6.3% for the vaginally delivered babies (P < 0.001). Therefore, higher prematurity rate in caesarean section group might be the main reason for higher TSH values in this group. Premature babies are more likely to have thyroid dysfunction due to several reasons including negative iodine balance. In our study, we have excluded premature babies to differentiate the effect of caesarean section itself on thyroid function tests. We have not found a significant difference in mean TSH concentrations in vaginally or C/S delivered babies (9.8±7.6 vs. 9.1±7.1 respectively at day 3). The findings of McElduf et al should be read with caution. References 1. McElduff A, McElduff P, Wiley V, Wilcken B 2005 Neonatal TSH as measured in a congenital hypothyroidism screening program: influence of the mode of delivery.J Clin Endocrinol Metab 90:6361-6363. 2. Turan S, Bereket A, Angaji M, Altun O, Unver T, Bilgen H, Akman I, Ozek E 2004 The Effect of the Mode of Delivery on Neonatal Thyroid Function and Neonatal Thyroid Screening. Horm Res 62 (Supp 2):189-190 (abst).