ESPE Abstracts

Background: Testosterone levels in newborns are changing over the first weeks of life. This dynamic change is making the assessment of infants with ambiguous genitalia complicated. The Clinical laboratory at Karolinska offer two different methods for measurement of serum testosterone, ECLIA (electrochemiluminescense immunoassay) and Liquid chromatography–tandem mass spectrometry (LC–MS/MS). It is important to evaluate these two methods in the neonatal period and the use of them in the diagnostic work-up in newborns with atypical genitalia or genital ambiguity.

Objectives: To measure testosterone in serum of newborn boys and girls, to obtain reference values of importance in the hormonal evaluation of a newborn with ambiguous genitalia. In addition, we wanted to see if genital masculinisation could be related to the testosterone levels in boys and girls respectively.

Method: Testosterone was analysed using two methods: ECLIA and LC–MS/MS. Blood sample were obtained from 45 full-term babies, at the same time as the neonatal screening sample, day 2–3. Clinical data in 100 babies for penis and clitoris length and Ano-genital distances (AGD) were collected using digital calipers. AGDas: anus to posterior base of scrotum, AGDap: to anterior base of penis, AGDaf: to fourchette, AGDac: to anterior base of clitoris.

Results: S-testosterone (ECLIA) in male full-term babies (N=20) mean 7.5 nmol/L (4.8–15.0 nmol/L). Female full-term (N=24) mean 5.1 nmol/L (2.0–7.8 nmol/L). S-testosterone (LC-MS/MS) in male full-term babies (N=22) mean 1.9 nmol/L (0.3–4.9 nmol/L). Female full-term (N=23) mean 0.2 nmol/L (0.1–0.6 nmol/L). Correlation between the ECLIA and the LC-MS/MS methods was moderate positive (Correlation coefficients 0,55). Penis length (N=52) mean 3.19 cm (2.15–4.15 cm) with no correlation between penis length and testosterone, neither method. AGDas/ap in males was 0.53 and with no correlation with testosterone. AGDaf/ac in females was 0.43 and there was a low negative correlation between AGDaf/ac and testosterone with the ECLIA method (Correlation coefficient −0.44) and no correlation with the LC-MS/MS method (Correlation coefficient −0.25).

Conclusion: Testosterone levels were, as expected, significantly higher in the boys. The ECLIA method gave testosterone varying between 2.0 and 7.8 in the girls, most likely due to cross reactivity with adrenal metabolites. The LC- MS/MS method gave considerably lower measurements. Knowledge on the normal levels of testosterone in the neonatal period is essential and valuable for adequate evaluation when assessing babies with genital ambiguity.