17
Renin- angiotensin mechanism plays a main part in maintaining electrolyte balance
and blood volume. The core factors controlling aldosterone release include reninangiotensin system, the adrenocorticotropic hormone (ACTH) produced by pituitary gland, and increase in plasma potassium or decrease in plasma sodium, thereby
directly stimulating the adrenal cortex. Aldosterone is just one of the numerous
elements that affect sodium excretion. While other main elements comprise atrial
natriuretic peptide, glomerular filtration rate, and alterations in renal tubular reabsorption of sodium (independent of aldosterone). The main function of the aldosterone secretion mechanism may be to maintain the intravascular volume, although
several other mechanisms are involved [6].
Pineal Gland
Pineal gland (epiphysis or pineal body) is a tiny ductless gland in brain. This is situated close to the midpoint of brain between hemispheres and is hidden in a groove
connected by two circular thalamus bodies. The pineal gland appears to be a redgray body having a size of a pea about 8 mm in human beings. It is positioned
behind and below the stria medullaris, outside of the superior colliculus, and amid
of laterally positioned thalamic bodies. This is part of upper epitheliums. As pineal
gland is a midline structure, so this can generally observe in calcified skull X-rays.
Melatonin is the chief hormonal secretion of pineal gland. The discharge is at its
peak level between 0 and 5 years old and at night time [27].
The Gonads
The gonads comprise testes and ovaries that have two main roles: (a) production of
germ cells (sperm by testes and eggs in ovaries) (b) they synthesize steroidal sex
hormones. These hormones are involved in development and functioning of male
and female sex organs as well as secondary features (e.g., male facial hair) and
pregnancy, delivery, and breastfeeding. There are three categories of sex hormones,
each regulating a discrete function. Sex hormones also play many important roles in
the body in addition to reproductive function. For instance, they have effect on
metabolism of lipid and carbohydrates, growth and development of bones and cardiovascular system [28].
Estrogens
Estrogen is mainly estradiol that is formed principally within ovaries except for a
small amount of estrone and estriol. Other synthesis sites for estrogen exist in corpus luteum, adrenal gland, and placenta. In postmenopausal women as well as in
1 Physiology of Endocrine System and Related Metabolic Disorders
Renin- angiotensin mechanism plays a main part in maintaining electrolyte balance
and blood volume. The core factors controlling aldosterone release include reninangiotensin system, the adrenocorticotropic hormone (ACTH) produced by pituitary gland, and increase in plasma potassium or decrease in plasma sodium, thereby
directly stimulating the adrenal cortex. Aldosterone is just one of the numerous
elements that affect sodium excretion. While other main elements comprise atrial
natriuretic peptide, glomerular filtration rate, and alterations in renal tubular reabsorption of sodium (independent of aldosterone). The main function of the aldosterone secretion mechanism may be to maintain the intravascular volume, although
several other mechanisms are involved [6].
Pineal Gland
Pineal gland (epiphysis or pineal body) is a tiny ductless gland in brain. This is situated close to the midpoint of brain between hemispheres and is hidden in a groove
connected by two circular thalamus bodies. The pineal gland appears to be a redgray body having a size of a pea about 8 mm in human beings. It is positioned
behind and below the stria medullaris, outside of the superior colliculus, and amid
of laterally positioned thalamic bodies. This is part of upper epitheliums. As pineal
gland is a midline structure, so this can generally observe in calcified skull X-rays.
Melatonin is the chief hormonal secretion of pineal gland. The discharge is at its
peak level between 0 and 5 years old and at night time [27].
The Gonads
The gonads comprise testes and ovaries that have two main roles: (a) production of
germ cells (sperm by testes and eggs in ovaries) (b) they synthesize steroidal sex
hormones. These hormones are involved in development and functioning of male
and female sex organs as well as secondary features (e.g., male facial hair) and
pregnancy, delivery, and breastfeeding. There are three categories of sex hormones,
each regulating a discrete function. Sex hormones also play many important roles in
the body in addition to reproductive function. For instance, they have effect on
metabolism of lipid and carbohydrates, growth and development of bones and cardiovascular system [28].
Estrogens
Estrogen is mainly estradiol that is formed principally within ovaries except for a
small amount of estrone and estriol. Other synthesis sites for estrogen exist in corpus luteum, adrenal gland, and placenta. In postmenopausal women as well as in
1 Physiology of Endocrine System and Related Metabolic Disorders