Variations in Biological and Immunological Activity of Growth Hormone during the Neonatal Period

Growth hormone deficiency and replacement in children

Growth hormone deficiency (GHD) is a rare but treatable cause of short stature. The diagnosis requires a careful evaluation of clinical history, physical examination and appropriate interpretation of longitudinal growth, with specific features for each period of life. Other clinical findings, in addition to growth failure, may be present and can be related to the etiology and to associated hormone deficiencies. Despite more than 50 years since the first reports of provocative tests of growth hormone (GH) secretion for the diagnosis of GHD, the interpretation of the results remains a matter of debate. When GHD is confirmed, GH treatment is recommended. Treatment is effective and safe, but requires daily injections during many years, which can affect adherence. At the end of longitudinal growth, during the transition phase, it might be necessary to re-evaluate GH secretion. This review summarizes and updates the recent information related to GHD in children, as well the recommendations for treatment.

Hypogonadotropic Hypogonadism in Infants with Congenital Hypopituitarism: A Challenge to Diagnose at an Early Stage

BACKGROUND

Combined pituitary hormone deficiency (CPHD) presents a wide spectrum of pituitary gland disorders. The postnatal gonadotropic surge provides a useful period to explore the gonadotropic axis for assessing the presence of congenital hypogonadotropic hypogonadism (CHH).

AIM

To explore the functioning of the hypothalamic-pituitary-gonadal axis in the postnatal gonadotropic surge for an early diagnosis of CHH in newborns or infants suspected of having CPHD.

SUBJECTS AND METHODS

A cohort of 27 boys under 6 months and 19 girls under 24 months of age with suspected hypopituitarism was studied. Serum concentrations of LH, FSH, testosterone, inhibin B, anti-Müllerian hormone (AMH) and estradiol were measured, and male external genitalia were characterized as normal or abnormal (micropenis, microorchidism and/or cryptorchidism).

RESULTS

CPHD was confirmed in 36 out of 46 patients. Low LH and testosterone levels were found in 66% of the hypopituitary males, in significant association with the presence of abnormal external genitalia. This abnormality had a positive predictive value of 93% for CHH. No significant association was observed between serum FSH, AMH and inhibin B and the patient's external genitalia.

CONCLUSION

In newborn or infant boys with CPHD, LH and testosterone concentrations measured throughout the postnatal gonadotropic surge, together with a detailed evaluation of the external genital phenotype, facilitate the diagnosis of CHH at an early stage.

Burden of Growth Hormone Deficiency and Excess in Children

Longitudinal growth results from multifactorial and complex processes that take place in the context of different genetic traits and environmental influences. Thus, in view of the difficulties in comprehension of the physiological mechanisms involved in the achievement of normal height, our ability to make a definitive diagnosis of GH impairment still remains limited. There is a myriad of controversial aspects in relation to GH deficiency, mainly related to diagnostic controversies and advances in molecular biology. This might explain the diversity in therapeutic responses and may also serve as a rationale for new "nonclassical" treatment indications for GH. It is necessary to acquire more effective tools to reach an adequate evaluation, particularly while considering the long-term implications of a correct diagnosis, the cost, and safety of treatments. On the other hand, overgrowth constitutes a heterogeneous group of different pathophysiological situations including excessive somatic and visceral growth. There are overlaps in clinical and molecular features among overgrowth syndromes, which constitute the real burden for an accurate diagnosis. In conclusion, both GH deficiency and overgrowth are a great dilemma, still not completely solved. In this chapter, we review the most burdensome aspects related to short stature, GH deficiency, and excess in children, avoiding any details about well-known issues that have been extensively discussed in the literature.

Different long-term response to growth hormone therapy in small- versus appropriate-for-gestational-age children with growth hormone deficiency

BACKGROUND/AIMS

The role of birth weight on growth hormone (GH) therapy response in GH-deficient (GHD) children has not been fully elucidated. Therefore, we examined the growth of 23 small-for-gestational-age GHD children (SGA-GHD, 11 females and 12 males), 26 appropriate-for-gestational-age GHD children (AGA-GHD, 11 females and 15 males) during the first 5 years of GH therapy and that of 22 non-GH-treated SGA children (12 females and 10 males).

METHODS

We collected height and height velocity measurements yearly.

RESULTS

In AGA-GHD children, height was always greater than in the SGA groups and significantly increased from the fourth year of treatment. Height velocity was higher (SGA-GHD: 1.72 ± 0.30 standard deviation score, SDS, AGA-GHD: 2.67 ± 0.21 SDS; p = 0.039) in AGA-GHD children during the first year of treatment. The AGA-GHD group showed the highest percentage (52.4%) of subjects surpassing mid-parental height and the greatest height gain after 5 years of follow-up.

CONCLUSION

Our results show that birth size is an important factor affecting the response to GH therapy in GHD children during the first 5 years of treatment. The paediatric endocrinologist should be aware of this factor when planning the management of GHD children born SGA.

Evaluation of the biological activity of human growth hormone by enzyme linked immuno-receptor assay (ELIRA) method

The aim of this research was to study the application and effectiveness of Enzyme Linked Immuno Receptor Assay (ELIRA) method for understanding the bioactivity of human Growth Hormone (hGH) in micro-titer plates. For this purpose, rabbit hepatocyte microsomes which contained hGH receptors were used for coating of ELISA micro-titer plates. Then hGH was interacted with coated receptors. Fractions of bounded complexes were identified by antibodies in an Enzyme-based substrate detection system. Different assay conditions such as: buffers, blocking agents, temperatures and times of incubation were analyzed. Our result indicated that, the carbonate coating buffer was not effective in receptor coating in ELIRA. Overnight incubation of hGH and hGH receptors in HEPES assay buffer and BSA blocking resulted in the lower linearity and correlations (R(2) = 0.46 to 0.85). However, 3 h incubation in Tris-HCl assay buffer at 30°C resulted in higher linearity and correlations (R(2) = 0.95 to 0.97). Finally, the coating of microwells by 250 μg/ml of microsome membranes in Tris buffer at 30°C for 3 hr and blocking by skim milk resulted to the best linearity and higher correlation, (R(2) = 0.985) and lower detection limit about 2 ng/ml of bioactive hGH.

Growth hormone, insulin like growth factor-1, and insulin-like growth factor-binding protein-3 levels in the neonatal period: a preliminary study

BACKGROUND

Growth hormone (GH), insulinlike growth factor-1 (IGF-1), and IGF-binding protein-3 (IGFBP-3) are used in the neonatal period for evaluation of diseases such as GH deficiency, intrauterine growth restriction, and hypoglycemia. However, GH level has been reported as a single value during the neonatal period. In this study, we attempted to determine the changes of GH, IGF-1, and IGFBP-3 in the neonatal period for each week.

METHODS

One hundred and two appropriate-for-gestational age (AGA) term neonates who did not have any diseases that would interfere with GH-IGF axis were included in this cross-sectional study. Blood samples were collected and serum GH, IGF-1 and IGFBP-3 levels were measured by immunoradiometric analysis (IRMA) and weekly values were obtained for the first postnatal four weeks.

RESULTS

We showed that GH level [median (1st-3rd quartile)] decreases from the first to the fourth postnatal week [25.1 (18.5-37.4); 17.2 (13.2-22.8); 17.6 (12.2-20.2); 14.4 (6.60-19.8) ng/mL, respectively)], IGF-1 and IGFBP-3 levels [median (lst-3rd quartile)] increase [41.7 (18.0-70.0); 55.9 (39.0-103); 53.0 (40.0-97.7); 71.7 (44.3-137) and 1852 (1597-2451); 2430 (1645-2838); 2841 (2280-3675); 3018 (2151-4189) ng/mL, respectively)].

CONCLUSIONS

GH, IGF-1 and IGFBP-3 values can be evaluated for each week separately instead of for the entire neonatal period.