Analysis of the GH content within archived dried blood spots of newborn screening cards from children diagnosed with growth hormone deficiency after the neonatal period

Estimation of the reference values and decision limits for growth hormone in newborns using dried blood spots

OBJECTIVES

Severe deficiency of growth hormone (GHD) of the newborn is a rare but potentially life-threatening disease. GH measured during the first week of life, using dried blood spots (DBS), may offer several advantages. Aim of the study was to estimate the reference values for GH in newborns by a new analytical method using DBS.

METHODS

Using a new developed analytical method, GH was estimated from DBS of 1,036 healthy newborns attending the Neonatology Unit of Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico of Milan in the period July-October 2021. Reference values for GH deficiency were estimated by the Harrell-Davis bootstrap method, with 90 %CI calculated by the bias-corrected and accelerated bootstrap method.

RESULTS

All GH measurements required 33 analytical sessions (8 months) with a CV% for calibration curve slopes equal to 6.9 %. Intermediate precision evaluated by measurement of low (3 μg/L) and high (10 μg/L) quality controls was, respectively, 14 and 6.5 %. GH reference values, estimated at percentiles 1.0st, 2.5th and 5.0th, and their 90 %CI, were, respectively, 4.5 μg/L (90 %CI 3.8-5.1), 5.9 μg/L (90 %CI 5.4-6.4) and 7.0 μg/L (90 %CI 6.7-7.3). GH levels were not associated with sex, standard deviation scores, birth weight, gestational age, type of delivery or mother's variables (age, smoking habit, gestational diabetes).

CONCLUSIONS

Validation data suggest that this method can be used to measured GH in newborns using DBS. The reference values estimated in this study are in accordance with previous published works using ELISA and may help confirming the clinical suspicion of neonatal GHD.

Diagnosis of severe growth hormone deficiency in the newborn

OBJECTIVE

Severe neonatal growth hormone deficiency (GHD) can cause recurrent hypoglycaemia. Early diagnosis is warranted. The aim of the study was to analyse the GH content in screening cards of 25 affected and 281 healthy newborns.

PATIENTS AND MEASUREMENTS

A total of 110 screening cards from ill newborns were sent to us for measuring GH content by a highly sensitive GH ELISA. Clinical information was obtainable in 61 cases. Severe GHD was defined by the presence of recurrent hypoglycaemia with a significant pituitary malformation or two additional pituitary hormone deficiencies. Screening cards from 281 healthy newborns (34.0-37.9 weeks) were prospectively analysed.

RESULTS

In 25 newborns (5 preterm), the definition of severe GHD was fulfilled based on recurrent hypoglycaemia in combination with malformation of the pituitary or midline structures in 21 cases and combined TSH and ACTH deficiency in four cases. The median GH concentration of those affected with severe GHD was 3.9 µg/L (range: 1.1-11.8), significantly below the previously reported reference range (P < .001). A GH concentration of 7 µg/L was confirmed as the cut-off for term newborns with the best accuracy (90.0% sensitivity and 98.7% specificity). The 95% reference range for healthy preterm newborns (n = 151) was 7.6-47.1 µg/L (median: 20.3 µg/L).

CONCLUSIONS

A GH content <7.0 µg/L in the newborn screening card confirms severe GHD with high accuracy. In preterm newborns, the lower limit of the reference interval was 0.6 µg/L higher than in term newborns. The newborn screening card is a valuable source for the very early diagnosis of GH deficiency.

Neonatal Hypopituitarism: Approaches to Diagnosis and Treatment

Hypopituitarism is defined as a decreased release of hypophyseal hormones, which may be caused by disease of the pituitary gland disease or hypothalamus. The clinical findings of neonatal hypopituitarism depend on the causes and on presence and extent of hormonal deficiency. Patients may be asymptomatic or may demonstrate non-specific symptoms, but may still be at risk for development of pituitary hormone deficiency over time. Patient history, physical examination, endocrinological, radiological and genetic evaluations are all important for early diagnosis and treatment. The aim of this paper was to present a review of etiological factors, clinical findings, diagnosis and treatment approaches in neonatal hypopituitarism.

Congenital Hypopituitarism

Mutations of growth hormone genes and pituitary transcription factors account for a small proportion of cases of severe congenital hypopituitarism. Most cases show characteristic MRI findings of pituitary stalk interruption syndrome. Clinical suspicion should prompt assessment of cortisol, free T4, thyroid-stimulating hormone, and growth hormone levels together with MRI of the hypothalamic and pituitary regions.

Adding Glucagon-Stimulated GH Testing to the Diagnostic Fast Increases the Detection of GH-Sufficient Children

BACKGROUND/AIMS

The evaluation of children with unexplained hypoglycemia may include a diagnostic fast. However, low growth hormone (GH) concentration during hypoglycemia is not specific to GH deficiency (GHD). The aim of this study was to determine if serial GH measurement following glucagon administration, in the setting of a diagnostic fast, would increase the number of children identified as not having GHD.

METHODS

We conducted a retrospective chart review of children who had serial GH measurements performed after glucagon administration at the end of a diagnostic fast. Glucagon was administered at the end of the fasting study, and GH was measured every 30 min for 210 min.

RESULTS

Of the 29 children in this series, only 3 (10%) had GH concentrations >7 ng/ml at the end of the fast, which increased by 16 (55%) after serial GH testing. The percentages of samples with GH concentrations >7 ng/ml were: 10% at baseline, and 25, 39, 41, 41, 33, 43, and 0% every 30 min thereafter.

CONCLUSION

Additional GH measurements after glucagon administration following a diagnostic fast can improve the identification of children without GHD and thereby save them unnecessary GH stimulation testing and potential GH treatment.