7
controlling of all secretions of pituitary gland together with various internal processes [5]. After receiving signals from systemic receptors, hypothalamus controls
the physical and chemical characteristics of the blood such as blood pressure, nutrition, temperature, and water content. Whenever there is alteration in the homeostatic function or some other developmental alterations are needed, a cellular
activity is induced by hypothalamus in desired body areas by stimulating release of
pituitary hormones. Stimuli or signals from approximately entire areas/parts of nervous system are received by hypothalamus that is itself negatively controlled by
pituitary regulatory hormones [1, 5].
Anterior Pituitary Gland’s Hormones
Growth Hormone
Release of growth hormones from anterior pituitary is being controlled by hypothalamus. Hypothalamus secretes both inhibitory hormone [growth hormone releasing inhibitor (GHRIH) or somatostatin] and secretary hormone [growth hormone
releasing hormone (GHRH)] into the hypothalamohypophyseal portal system. Both
IGF-1 and GH negatively respond to pituitary gland and hypothalamus [6]. Negative
feedback regulatory mechanism of hormones regulated by frontal lobe of pituitary
gland is illustrated in Fig. 1.3. The stimuli which increase the growth hormone
secretion are categorized as:
• Elevated quantities of peculiar amino acids (A.A) in plasma
• Hypoglycemia and fasting
• Stressful/distressing stimuli
The secretion of growth hormone (GH) decreases with increasing levels of glucose, cortisol, and free fatty acids (FFA) in the plasma as well as during rapid eye
movement sleep. The main functions of GH include the following:
• It stimulates the growth of bone, cartilage, and soft tissue by the action of IGF-1
(insulin-like growth factor or formerly known as hormone C). Its secretion in the
liver, kidney, and other tissues is increased in response to GH.
• It stimulates the mobilization of fat by releasing fatty acids from adipose tissue.
• It increases the rate of protein synthesis in all body cells.
• Hepatic glucose output is increased by GH.
• The rate of glucose consumption is reduced all over the body due to reduced
uptake of glucose by cells (i.e., it is counter regulatory to insulin).
• K+ and Na+ excretion are decreased, while Ca2+ absorption from the intestine is
increased.
• It promotes erythropoiesis [7].
1 Physiology of Endocrine System and Related Metabolic Disorders
controlling of all secretions of pituitary gland together with various internal processes [5]. After receiving signals from systemic receptors, hypothalamus controls
the physical and chemical characteristics of the blood such as blood pressure, nutrition, temperature, and water content. Whenever there is alteration in the homeostatic function or some other developmental alterations are needed, a cellular
activity is induced by hypothalamus in desired body areas by stimulating release of
pituitary hormones. Stimuli or signals from approximately entire areas/parts of nervous system are received by hypothalamus that is itself negatively controlled by
pituitary regulatory hormones [1, 5].
Anterior Pituitary Gland’s Hormones
Growth Hormone
Release of growth hormones from anterior pituitary is being controlled by hypothalamus. Hypothalamus secretes both inhibitory hormone [growth hormone releasing inhibitor (GHRIH) or somatostatin] and secretary hormone [growth hormone
releasing hormone (GHRH)] into the hypothalamohypophyseal portal system. Both
IGF-1 and GH negatively respond to pituitary gland and hypothalamus [6]. Negative
feedback regulatory mechanism of hormones regulated by frontal lobe of pituitary
gland is illustrated in Fig. 1.3. The stimuli which increase the growth hormone
secretion are categorized as:
• Elevated quantities of peculiar amino acids (A.A) in plasma
• Hypoglycemia and fasting
• Stressful/distressing stimuli
The secretion of growth hormone (GH) decreases with increasing levels of glucose, cortisol, and free fatty acids (FFA) in the plasma as well as during rapid eye
movement sleep. The main functions of GH include the following:
• It stimulates the growth of bone, cartilage, and soft tissue by the action of IGF-1
(insulin-like growth factor or formerly known as hormone C). Its secretion in the
liver, kidney, and other tissues is increased in response to GH.
• It stimulates the mobilization of fat by releasing fatty acids from adipose tissue.
• It increases the rate of protein synthesis in all body cells.
• Hepatic glucose output is increased by GH.
• The rate of glucose consumption is reduced all over the body due to reduced
uptake of glucose by cells (i.e., it is counter regulatory to insulin).
• K+ and Na+ excretion are decreased, while Ca2+ absorption from the intestine is
increased.
• It promotes erythropoiesis [7].
1 Physiology of Endocrine System and Related Metabolic Disorders