medwireNews: A study of preterm boys shows increased androgen levels at the estimated time of birth in those with low birthweight (LBW).
Moreover, catch-up in weight to a corrected age of 10 months was significantly associated with testosterone and androstenedione levels at that age.
“Whether our results are also applicable to full-term boys merits further studies”, the researchers write in The Journal of Clinical Endocrinology & Metabolism.
The team studied 98 boys born at gestational age 32.0 to 36.9 weeks and found the expected rise in testosterone after birth; it peaked at 2 months’ corrected age (3 months’ chronological age) and then declined to the end of follow-up at the corrected age of 10 months, at which point 83 boys remained in the study.
Kerstin Allvin (Sahlgrenska University Hospital, Gothenburg, Sweden) and study co-authors also found that dihydrotestosterone (DHT) followed the same pattern. Moreover, testosterone and DHT levels strongly correlated throughout follow-up.
The researchers say theirs is the first study to report changes in DHT in infant boys using mass spectrometry. This technique is more accurate than the immunoassays used in some previous studies, they say, adding that their prospective study design allowed them to “capture the dynamic changes during infancy.”
Both testosterone and DHT correlated negatively with birthweight and weight standard deviation score (SDS) at 0 months’ corrected age. At 0 months, the 47 boys with a low birthweight (LBW; <2500 g) had significantly higher levels of both these androgens compared with boys who had a normal birthweight, at medians of 5.7 versus 3.5 nmol/L for testosterone and 1.2 versus 0.9 nmol/L for DHT.
At birth, the LBW boys were significantly smaller than other boys in terms of weight, height and head circumference, but by the age of 10 months (corrected) the only remaining difference was weight, with the median SDS being –0.49 versus +0.30. Catch-up in weight SDS correlated with levels of testosterone and androstenedione at 10 months.
Allvin and team say research to date suggests that “LBW and prematurity seems to enhance and prolong the minipuberty period.”
They add: “It therefore seems logical that the boys born with LBW in the present study, who were all preterm, presented with increased testosterone levels around [the estimated delivery date].”
Levels of androstenedione, oestrone and oestradiol declined between birth and 10 months. Androstenedione levels did not differ between birthweight groups, while the oestrogens were lower in LBW boys at birth only.
Finally, insulin-like growth factor (IGF)-1 levels declined between 2 and 5 months’ corrected age, before increasing at month 10. At birth, this was significantly lower in LBW boys than those with a higher birthweight (median 34 vs 59 µg/L) but higher at month 5 (median 48 vs 34 µg/L).
IGF-1 levels correlated positively with weight SDS and inversely with testosterone and DHT in the overall cohort, and the researchers speculate that both IGF-1 and testosterone “may be beneficial for optimizing catch-up growth in boys born after intrauterine growth restriction”.
By Eleanor McDermid
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