**2. Growth hormone**

Growth hormone (GH), also known as somatotropin, is a hormone that regulates healthy body development and growth. This process is made possible by accelerating the creation of protein in muscle cells and the release of energy from the breakdown of fat. A number of hormones are crucial to human development (GH), also known as somatotropin [20]. It is a 191 amino acid protein that the anterior pituitary gland secretes to regulate healthy growth and development, as depicted in the **Figure 1**. Human growth is divided into two phases. One at conception, the other at puberty. GH is important in these two stages [22]. Every day of a normal person's life,

**Figure 1.** *Growth hormone [21].*

amounts of GH are detectable. Nevertheless, because eating and activity have an impact on GH levels, they change throughout the day. There are GH-responsive receptors on the cells and tissues of the body [13]. The metabolic effects of GH are in muscle, liver, and fat cells, which are crucial to their function, but the visible effect of GH is on linear skeletal development [23]. There are two types of GH in humans. It's unclear how the two vary functionally, though. Although they are both products of the same gene, one of them lacks the amino acids between positions 32 to 46 [24] in Thongh.

Somatotrophs in the anterior pituitary gland create growth hormone (GH) under the guidance of hormonal signals in the hypothalamus [25]. GH is regulated by two hypothalamic hormones. GHRH (growth hormone-releasing hormone) and GHIH (growth hormone-inhibiting hormone) are the two (GHIH). This procedure' mechanism may be fully explained. As a result, when blood glucose levels decrease. The secretion of reserve GH is induced by GHRH. GHRH release is inhibited as blood glucose levels rise [26]. The effect is comparable when blood protein levels rise. This hypothalamic feedback loop causes GH levels to change during the course of the day. 1 to 3 ng/ML of normal plasma GH levels. The hormones insulin, glucagon, and adrenaline also control the availability of plasma glucose and amino acids for growth [27]. GH is primarily released during night. At 10 o'clock, midnight, and 2 a.m., GH release peaks. The rationale behind this time of day is that other hormones, such as the somatomedins, IGH-1 and IGH-2, mediate the majority of GH effects. As a result, GH's effects are more uniformly distributed throughout the day [25]. Due to their vital involvement in the production of GH and other hormones, a number of hormonal disorders can result in excessive or reduced development. However, a pituitary tumor frequently results in abnormal growth. Underproduction of GH, a deficiency in IGH-1, or a problem with the target tissue's reaction to either of these growth hormones can all contribute to dwarfism (extremely short stature). Gigantism and acromegaly, both of which are characterized by a very enormous stature, can result from an excessive production of GH or IGH-1, or from an exaggerated response to these hormones [28]. Early childhood overproduction of GH, which can result in gigantism, can generate skeletal heights of up to 8 feet (2.5 meters) or more [3]. When GH is overproduced after the onset of puberty, acromegaly develops. The body's long bone's epiphyseal plates are unable to close in this situation. In addition, they continue to respond to GH-stimulated further growth. An enlarged nose, throat, tongue, hands, feet, and cranium are features of this condition [28].

#### **2.1 Growth hormone chemistry**

A single chain polypeptide hormone of 191 amino acids and a molecular weight of 22,000 Daltons, human growth hormone is depicted in **Figure 2**. Four helices in the structure are required for a proper interaction with the GH receptor [31]. Growth hormone, chorionic somatomammotropin (placental lactogen), and prolactin have similar sequences.

Only the placenta secretes the 22-KD GH variant (hGH-V), which differs from pituitary GH by 13 amino acids [32]. Approximately 75% of the pituitary's typical GH secretion is in the mature 22-KD form. The loss of amino acids 32 to 46 caused by the second codon's alternative splicing produces in a 20 KD variant, which normally makes up 5 to 10% of pituitary GH.

*Carbohydrate Metabolism in Growth Hormone Therapy for Children DOI: http://dx.doi.org/10.5772/intechopen.110778*

#### **Figure 2.**

*Structure of growth hormone [29]. Pituitary GH is also found in deaminated and N-acetylated forms, as well as different GH oligomers [30].*

#### **2.2 Secretion of GH**

Growth hormone (GH) is secreted into the blood by the somatotrope cells in the anterior pituitary gland as shown in the **Table 1**, more than any other pituitary hormone in significant quantities. These cells' growth and GH synthesis are both accelerated by the transcription factor PIT-1. GH shortage is the result of the anterior pituitary gland being destroyed and these cells failing to grow [33]. The main regulators of GH secretion by somatotropes are peptides produced by neurosecretory nuclei of the hypothalamus into the portal venous circulation surrounding the pituitary. Arcuate nucleus growth hormone-releasing hormone (GHRH) and Somatostatin from the periventricular nucleus suppresses GH secretion while ghrelin promotes it.


**Table 1.** *Secretion of growth hormone.*

Negative feedback from circulating GH and IGF-1 concentrations also affects GH secretion [20]. Even though the ratio of this stimulating to inhibitory peptide regulates GH release, various physiological stimulators and inhibitors of GH secretion can alter this ratio. Among other things, sleep, exercise, hypoglycemia, dietary protein, and estrogen are stimulators of GH secretion. Glucocorticoids and dietary carbohydrates are GH secretion inhibitors [22]. Throughout life, GH secretion follows a different rhythm. Early childhood has the highest basal levels. During the pubertal development spurt, the amplitude and frequency of peaks are at their highest. A healthy youngster or adolescent experiences eight peaks on average every day. Adults typically have five peaks. Throughout adulthood, basal levels, as well as the frequency and amplitude of peaks, decrease [34].

### **2.3 Function of GH**

The actions of growth hormone on the body's tissues are referred to as anabolic effects (building up). GH, like the majority of other protein hormones, works by binding to a specific receptor on the surface of cells. The most well-known effect of GH activity is childhood height growth. There are at least two processes that seem to promote it [20]. Direct stimulation from GH causes cartilage chondrocytes to divide and multiply. These are the main cells of children's growing long bones (arms, legs, and digits), known as epiphyses [22]. In addition, GH promotes the synthesis of the proinsulin-like hormone insulin-like growth factor 1 (IGF 1, originally known as somatomedin C). The liver, which is the main location of IGF-1 synthesis, is a significant target organ of GH in this process. According to the table, IGF-1 exerts growthstimulating effects on a range of tissues as shown in the **Table 2**. Target tissues produce more IGF-1, demonstrating that it is both an endocrine and an autocrine/ paracrine hormone [22]. Although height growth is the most well-known consequence of GH, it also performs a variety of other metabolic tasks. GH improves bone mineralization, bone strength, and calcium absorption. Additionally, it builds muscle. Additionally, it stimulates the body's many organ systems to expand and produce more protein, creating a "positive nitrogen balance". GH boosts immunological function [20]. GH's part in maintaining fuel homeostasis. A counterproductive impact of GH was a reduction in the liver's absorption of glucose. It also helps keep pancreatic islets healthy and functioning. GH tends to encourage lipolysis, which causes a small decrease in adipose tissue (body fat) and an increase in the blood's levels of free fatty acids and glycerol [33].


**Table 2.** *Effect of growth hormone.*
