We read the article by Chittawar, et al. [1],
and would like to appreciate the authors for highlighting the important
but under-recognized pitfalls in sampling and interpretation of
endocrinology reports of neonates. However, there are certain points we
would like to highlight, which might bring more clarity in interpreting
endocrine values in neonates.
1. The total calcium values are slightly lower in
neonates; however, ionized calcium values are comparable to older
children and adults [2]. The low total calcium values are due to low
serum protein levels. Therefore, correction formulas/nomograms to
convert total calcium into ionized calcium may not be valid in
neonates.
2. Authors stated that the cut-off for the
diagnosis of hypoglycemia is £45
mg/dL in first 24 hours. There is no mention whether it is blood
glucose or plasma glucose. As per recent recommendations of
Pediatric Endocrine Society, during first 48 hours of life, plasma
glucose target should be >50 mg/dL, and after 48 hours it should be
60 mg/dL [3].
3. With increasing survival, evaluation of
extreme preterm babies with maternal hypothyroidism is an upcoming
challenge. There is very less normative data in extreme preterm
neonates. Currently most commonly used absolute cut-offs for
hypothyroidism are T4 <6.5 ug/dL and TSH >20 mU/L. However, as per
the available data in this population (23-27 weeks), the normal TSH
value is 0.2-30.3 mU/L and normal mean T4 is as low as 4 ug/dL [4].
Therefore, before labeling as hypothyroidism and starting therapy,
one must see gestation and postnatal age-specific nomograms.
4. Level of growth hormone, IGF-I, and IGFBP-3 at
birth are significantly different in intrauterine growth restricted
(IUGR) babies compared to appropriate for gestation age (AGA) babies
[5]. As per WHO 2013 report, 47% of babies in India are small for
gestational age (SGA), and out of which about 10% will remain short
and need evaluation. Also, these are the babies who will have
persistent hypoglycemia, and as a part of the evaluation will
undergo growth hormone testing. Therefore, one must use
IUGR-specific values while interpreting growth hormone values.
Last but not the least, while interpreting values,
due attention must be given to units of the reported values and
appropriate conversion factor should be used wherever required to avoid
analytical errors.
References
1. Chittawar S, Dutta D, Khandelwal D, Singla R.
Neonatal endocrine labomas - Pitfalls and challenges in reporting
neonatal hormonal reports. Indian Pediatr. 2017;54: 757-62.
2. Wandrup J, Kroner J, Pryds O, Kastrup KW.
Age-related reference values for ionized calcium in the first week of
life in premature and full-term neonates. Scand J Clin Lab Invest.
1988;48:255-60.
3. Thornton PS, Stanley CA, De Leon DD, Harris D,
Haymond MW, Hussain K, et al. Pediatric Endocrine Society.
Recommendations from the Pediatric Endocrine Society for evaluation and
management of persistent hypoglycemia in neonates, infants, and
children. J Pediatr. 2015;167:238-45.
4. Williams FLR, Simpson J, Delahunty C, Ogston SA,
Bongers-Schokking JJ, Murphy N, et al. Developmental trends in
cord and postpartum serum thyroid hormones in preterm infants. J Clin
Endocrinol Metab. 2004;89:5314-20.
5. Leger J, Noel M, Limal JM, Czernichow P. Growth factors and
intrauterine growth retardation. II. Serum growth hormone, insulin-like
growth factor (IGF) I, and IGF-binding protein 3 levels in children with
intrauterine growth retardation compared with normal control subjects:
prospective study from birth to two years of age. Study Group of IUGR.
Pediatr Res. 1996;40:101-7.
