Introduction

Growth hormone (GH), also called somatotropin, is a peptide hormone that is important for human development. It is responsible for stimulating growth, cell proliferation, and cell regeneration. The growth hormone also stimulates IGF-1 production and increases the concentration of glucose and free fatty acids (Greenwood & Landon, 1966; Ranabir & Reetu, 2011). Insulin-like growth factor 1 (IGF-1), also called somatomedin C, is a peptide hormone that plays a vital role in childhood development and has anabolic effects in adults. IGF-1 is produced mainly by the liver and is characterized by similarities in the molecular structure of insulin (Ewaid & Abed, 2017; Höppener et al., 1985).

Growth hormone deficiency (GHD) is a medical condition due to a lack of growth hormone if it begins in childhood or infancy, and is characterized by several symptoms, especially short stature. The cause of this condition is unknown in 75 percent of patients, and in most cases, brain malformations occur (Rikken et al., 1995; Salim & Abed, 2017). GHD may be isolated or combined with other anterior and/or posterior hormonal deficiencies. GHD has been found to be a rare but important cause of short stature in children (Dattani & Malhotra, 2019). The incidence of congenital GHD with male predominance is 1 out of 4000 to 1 out of 10,000 live births (Abed & Salim, 2019; Kautsar, Wit, & Pulungan, 2019; Salim & Abed, 2019).

Short stature is a term used for a child whose length is two standard deviation more or below the mean for children of that sex and age (Rogol, 2016). In fact, short stature is a common problem in children, and it may occur due to many causes such as genetic, environmental, or chronic diseases. Diagnosis of short stature can be accomplished in two concerted ways, physical examination and laboratory testing. Treatment for short stature mainly depends on the correct diagnosis and the causative agent (Albalawi et al., 2018).

The most important effect of growth hormone administration in humans is a marked increase in free fatty acids that influence the stimulation of lipolysis and ketogenesis after 1-2 hours. This stimulation constitutes a major physiological adaptation of stress and fasting (Møller, Gjedsted, Gormsen, Fuglsang, & Djurhuus, 2003). GHD has shown an increase in triglycerides and cholesterol (mostly LDL cholesterol). In fact, treatment for GH in children with GHD demonstrated unclear changes in cholesterol concentration (Abed & Salim, 2018; Cuneo, Salomon, McGauley, & Sönksen, 1992).

It has been reported that both GH and IGF-1 reduce hepatic ureagenesis and gene expression of urea cycle enzymes. These findings strongly suggest that GH and IGF-1, at least in part, have exercised their influence on the regulation of urea synthesis at the gene level, and this is necessary for the anabolic effects of GH and IGF-1 (Grøfte et al., 1997). In addition, GH can alter the level of creatinine in the blood by its anabolic effects on the muscles (Davani-Davari, Karimzadeh, & Khalili, 2019).

Growth hormone is one of the most potent anabolic agents. A previous study investigated the effect of GH on the concentration of urinary creatinine over a 24-hour period as an indication of muscle mass catabolism in burned patients. GH is effective in reducing creatinine excretion in the urine. It has been speculated that this lack of creatinine excretion in the urine may be associated with muscle catabolism (Akçay, Akçay, Solak, Balık, & Aylu, 2001). Growth hormone and insulin-like growth factor-I are two important physiological regulators for growth, body composition, and kidney function. The disorder of the GH-IGF-1 axis is responsible for many important complications that appear in chronic kidney diseases (CKD), such as growth retardation and cachexia (Mak, Cheung, & Roberts, 2008). In animals, anterior pituitary insufficiency causes decreased GFR, and it was found that this phenomenon is reversible after the administration of GH. In patients with hypophysectomized, when a substitutive therapy is given for all hormones in the pituitary gland, GFR will decline without any parallel change in the extracellular size (Grunenwald, Tack, Chauveau, Bennet, & Caron, 2011).

Currently, the diagnosis of growth hormone deficiency is based on clinical, biochemical, and neuroradiological studies. The Clonidine Test (CT) is widely used to assess the state of growth hormone secretion (Ibba et al., 2018). To confirm GHD, provocative tests of GH secretion using psychological/pharmacological stimuli are required. In this work, the relationship between the expected disturbance in lipid profile and other parameters such as urea and creatinine on the etiology of short stature in children and adolescents were studied.

Materials and Methods

Subjects and study design

This study includes one hundred and twenty subjects from children to adolescents with an age range between (4-18) years. Among them were sixty healthy individuals as a control group, male and female, and sixty short stature patients with growth hormone deficiency.

These subjects were selected from outpatients who were attended to the Pediatric department/National Diabetic Center (NDC)/Mustansiriyah University, Baghdad, Iraq.

The patients were diagnosed by an endocrinology specialist as a short stature with growth hormone deficiency.

Sample Collection

From each individual, 10 ml of blood was drawn through a vein puncture using disposable syringes and collected in a gel tube. Blood samples were collected from each subject between 8-11 a.m. after overnight fasting. After collection, the blood samples were centrifuged at 3000 rpm for 10 minutes.

The resulting serum was stored at -20 ℃ until the time of analysis. Samples were analyzed at the National Center for Diabetes and Endocrinology at Mustansiriyah University.

Sample Analysis

The body mass index (BMI) was calculated from the subjects studied by the following formula: BMI = weight (kg) / length (m²)

BMI Percentiles assort the position of an individual by indicating the percentage of the reference population that the individual is equal to or exceeds. The BMI percentile can be calculated via a BMI calculator or by a growth chart represented previously (Walker, Clark, Cranswick, Johnson, & Jones, 2002). The BMI was categorized based on age-and sex-specific values of the 2,000 Centers for Disease Control and Prevention (CDC) growth charts. The categories were underweight (<5th percentile), normal weight (5th to 84th percentile), overweight (85th to 94th percentile), and obese (≥95th percentile) (Barlow, 2007).

Serum GH and IGF-1 levels were estimated by a sandwich chemiluminescence immunoassay (CLIA) following the protocol of the available kits supplied by (DiaSorin/Italy). Levels of lipid profile (cholesterol, triglyceride, and HDL), creatinine, and urea were estimated enzymatically using the colorimetric assay following the protocol of the available kits supplied by BIOLABO/France. Levels of LDL and VLDL were calculated according to the Friedewald equation.

Statistical analysis

Data was analyzed using SPSS statistical software, version 26. Independent-Samples Student t-test was performed between patients and control groups, and the resulting values ​​were expressed as mean ± standard deviation (SD). The Pearson correlation coefficient was also carried out to determine the relationships between all study variables.

The statistical tests were significant at p<0.05 and highly significant at p<0.01 with a confidence interval of 95%.

Results and Discussion

All anthropometric data obtained from patients with growth hormone deficiency and the control group are summarized in Table 1. The results showed a highly significant decrease (p<0.01) in the mean values ​​of patients weight and length (27.73 ± 11.65 kg, 122.52 ± 16.48 cm) compared to the control values ​​(33.78 ± 11.94 kg, 134.50 ± 17.47 cm). Additionally, BMI results revealed a non-significant difference (p>0.05) between patients (17.62 ± 3.63 kg/m²) and control groups (18.11 ± 2.00 kg/m²).

The results revealed that the study cases, both for children and adolescents, were in the same age range, and this is very important to give a real comparison between patients and control groups. The results obtained in this study are consistent with the results of a previous study (Ece et al., 2014), which stated that the weight was lower in patients with a growth hormone deficiency, both children and adolescents, compared to the control group. However, the results are not consistent with the results of another study (Wang, Zhang, Cao, Kong, & Ge, 2019). Differences between studies can be due to differences in nutritional status, sample size, and lifestyle of the subjects. Likewise, a previous study (Bahrani, Aa, & Ak, 2011) identified a significant decrease in the height of children and adolescents with growth hormone deficiency compared to the control group. This result is because GHD is one of the reasons for short stature that affect bone maturation (Olney, 2003). The current BMI results are consistent with the results of a previous study (Lee et al., 2013) that reported non-significant differences in BMI between patients and the control group. This finding could be due to the fact that the BMI includes weight and height, and both of these are almost decreasing in the same range for both studied groups.

BMI percentile results showed a significant difference between patients and control groups, as shown in Table 2. The results are consistent with a previous study (Mikki, Abdul-Rahim, Awartani, & Holmboe-Ottesen, 2009)that stated that some GHD patients were underweight. This finding may be due to factors such as malnutrition, socioeconomic status, and patient gender (Tzanela et al., 2010). On the other hand, the reason for the high number of overweight cases in patients may be that GH has a lipolytic effect on adipose tissue, and patients with GH deficiency generally have abundant fat tissue. The current results are in good agreement with a previous study (Lee et al., 2013), which has shown that secretion of GH decreases in obese people, and both spontaneous and stimulated GH levels are low in patients with GH deficiency.

The data in Table 3 shows the levels of GH and IGF-1 in the studied groups for children, adolescents, and total. A non-significant difference (p>0.05) was found in basal GH between patients (0.53 ± 0.20 ng/ml) and control (0.58 ± 0.19 ng/ml).

While GH levels were found after 1 hour and 1.5 hours (provocation with clonidine) decreased significantly (p<0.01) in patients (2.81 ± 1.58 ng/ml) and (1.48 ± 1.09 ng/ml) compared to control values ​ (15.03 ± 4.28 ng/ml) and (7.22 ± 3.23 ng/ml), respectively. The results revealed that IGF-1 levels were significantly reduced (p<0.01) in patients (128.40 ± 79.13 ng/ml) compared to control (233.65 ± 93.05 ng/ml). For details of the results of all children and adolescents, refer to Table 3.

The results presented here are consistent with a previous investigation (Bhagwat et al., 2018) that reported a non-significant difference between basal GH levels in patients and control. It may be due to the release of growth hormone, which is pulsated with diurnal variation, under a negative feedback autoregulation loop, and may be affected by various factors. Factors that affect the secretion of growth hormone include sleep, exercise, and physical stress such as fasting, hypoglycemia, hyperglycemia, and shock. Growth hormone secretion shows the differences between sexes, with pulsatile male secretion versus continuous female secretion. Moreover, the level of secretion also decreases with age, a phenomenon called somatopause (Ewaid, Abed, & Al-Ansari, 2020; Lim & Khoo, 2017).

Current results for levels of GH2 (after 1 hr.) and GH3 (after 1.5 hr.) correspond to the results reported in a previous study (Bhagwat et al., 2018). It may be due to the pulsatile way of GH secretion and the increase after the stimulation. Furthermore, the results of IGF-1 levels were consistent with a previous study (Al-Zaidy, Parisi, Abed, & Salim, 2019; Bahrani et al., 2011) who reported a significant reduction in IGF-1 levels among patients compared to healthy controls. It may be due to IGF-1 is a reliable marker of GH action and is affected by several factors such as age, gender, liver disease, and fasting state (Ewaid & Al-Ansari, 2019; Ewaid, Abed, & Al-Ansari, 2019; Mukherjee & Shalet, 2009).

Collective results describing the total values ​​of the measured parameters for the two study groups are summarized in Table 4. The results confirmed that there were no significant differences (p>0.05) in the HDL level (52.36 ± 5.48 mg/dL) of GHD patients comparing with the control values (53.00 ± 5.28 mg/dL). While, there were a significant increased (p<0.05) in triglyceride level of patients (88.70 ± 5.71 mg/dL) compared to the control (85.45 ± 9.72 mg/dL). This increase appears very clearly in children, while there is no difference in adolescents. Refer to Table 4. Furthermore, the results showed a non-significant increase (p>0.05) in LDL levels (91.59 ± 23.94 mg/dL) and cholesterol levels (161.70 ± 22.23 mg/dL) of patients compared to the control (83.46 ± 31.29 mg/dL) and ​​(153.55 ± 30.86 mg/dL), respectively. There was a significant increase (p<0.05) in VLDL levels in patients (17.74 ± 1.14 mg/dL) compared to control (16.09 ± 1.94 mg/dL), and it specifically appears in children. In addition, there were non-significant differences (p>0.05) in urea and creatinine levels between patients (26.88 ± 4.19 mg/dL, 0.79 ± 0.24 mg/dL) and control values ​​(27.36 ± 3.95 mg/dL, 0.72 ± 0.19 mg/dL), respectively, bearing in mind that there is a significant increase in creatinine level of adolescents patients.

The results obtained in this study are consistent with previously reported results (Stawerska, Smyczyńska, Hilczer, & Lewiński, 2017), which showed non-significant differences in cholesterol and HDL levels and a significant increase in triglyceride and VLDL levels in patients with growth hormone deficiency compared to control. While the results disagree with the results of another study (Evans et al., 2000) that stated there were no differences in lipid profiles between GHD and controls. Regarding urea and creatinine levels, the current results are consistent with a previous study (Ece et al., 2014) that reported non-significant differences in urea and creatinine levels between GHD patients and control. Short stature is common in children with chronic renal insufficiency (CRI), and several reasons contribute to the pathogenesis including metabolic acidosis, water-electrolyte disturbances, protein malnutrition, and malnutrition with corticosteroid which create resistance to the action of GH (Abed et al., 2018; Hardin, 2008).

The correlation between all variables included in the current study was examined for GHD patients using Pearson correlation analysis, and the results were represented in Table 5. The results showed that the GH level was positively correlated with cholesterol and LDL levels. The analysis also revealed the presence of a positive correlation between the levels of GH and creatinine, especially in adolescent patients. Furthermore, the current study revealed a positive correlation of IGF-1 with urea levels.

The results showed a positive correlation between the levels of cholesterol and LDL and a positive correlation between the levels of TG with VLDL of patients with GHD. It also showed a negative correlation between the levels of LDL and HDL.

Conclusion

Valuable information is available on kidney function and lipid profile, but its association with short stature disorder needs further study. This study shows a clear relationship between disturbances in creatinine and the promotion of GHD in short stature patients. The results indicated that serum creatinine level, more precisely in adolescents of GHD patients, is substantially affected relative to those in healthy subjects.

Current work has demonstrated that abnormalities in the lipid profile (especially triglycerides and VLDL) are closely associated with the etiology of short stature. Pearson correlation analysis revealed this demonstration, especially in children. Finally and most importantly, the results confirm that triglycerides in the blood and VLDL may help identify patients at an early age who are at risk of short stature (particularly children). More studies are recommended to understand the exact mechanism of the relationship between the lipid profile and creatinine with the short stature etiology.