The endocrine system has different endocrine glands situated at different location in our body.
These are: pituitary, pineal, thyroid, adrenal, pancreas, parathyroid, thymus, gonads: in males testis, in female ovary, are the organised endocrine bodies in our body. Also, the following produce hormones e.g., gastrointestinal tract, liver, kidney and heart. Let us study about these structures/organs.
Hypothalamus:
Hypothalamus is the basal part of the diencephalon, forebrain and it regulate a wide spectrum (range) of body functions. It has several groups of neurosecretory cells called nuclei which produce hormones. These hormones regulate the synthesis and secretion of pituitary hormones. Two types of hormones produced are:
1. Stimulating or release hormones that when released they stimulate the pituitary to release their secretions/ hormones. They are denoted as RA. e.g., Gonadotrophin releasing hormone: GnRH. This hormone stimulates the secretion of gonadotrophins synthesis and their release.
2. Inhibitory hormones that when released they check/ stop/inhibit the secretion of hormones, e.g., somatostatin hormones is a inhibiting hormone released by hypothalamus. It inhibits the release of growth hormone (GH) from the pituitary gland. These hormones originate the hypothalamic neurons passes through axons and are released at their nerve endings. When these hormones reach the pituitary gland through a portal circulatory system and regulates the functions of the anterior pituitary. Where as, the posterior pituitary is under the direct neural control of the hypothalamus.
The excess (hyper) secretion of hormones and less (hypo) secretion of hormones causes hormonal imbalance in the body and causes many disorders. This can be contracted by certain medicines.
1. Growth Hormone (GH): Excess secretion (hyper) of GH in adults and specially in middle age causes serious complications. The face is disfigured and this condition is known as acromegaly. It may also leads to death if it goes unchecked. It often goes undetected for many years, till external features are visible.
The less secretion of GH results in abnormal growth - stunted growth is called pituitary dwarfism. Thus, Gigantism (giant like body) and dwarf (small body) are two abnormalities due to GR secretion. To have a normal body growth GR should be produced in correct amount. Kyphosis is due to bending of back bone (vertibral column).
2. Prolactin (PRL/PL) : This hormone is responsible for growth of mammary glands and formation of milk in adult females.
3. Thyroid Stimulating Hormone (TSH): This hormone stimulates the synthesis and secretion of thyroid hormones from thyroid gland located in neck region. Less secretion of thyroid stimulating hormone causes goitre .
4. Adrenocorticotrophic hormone (ACTH): ACTH stimulates the secretion of steroid hormones known as glucocorticoids from the adrenal cortex that is located on top of kidneys like a cap/crown.
5. Lutetnizing hormone (LH) and Follicle Stimulating hormone (FSH): These hormones stimulate the gonads and hence, are also called gonadotrophins. LH in males stimulates the synthesis and secretion of hormones called androgens from testis (gonads). Where as FSH and androgens are responsible for regulating the sperm atogenesis (i. e., formation of sperms). In females LH induces the ovulation process (release of egg/ovum) the fully mature graafian follicles and maintains the corpus luteum (yellow spot) that secretes hormones. FSH stimulates growth and development of the ovarian follicles.
6. Metanocyte StimuLating hormone (MSH): The pigmentation of the skin (colour) is due to melanin contain cells called melanocytes. It is regulated by MSH.
7. Oxytocin: This hormone acts on the smooth muscles (involuntary muscles) of our body and stimulates their contraction. In females the stimulation for vigrous contraction of uterus during the time of child birth. It also helps in ejection of milk after child birth from mammary glands.
8. Vasopressin: It is also called anti - diuretic hormone (ADH). It controls the reabsorption of water and electrolytes from the distal tubules (DT) or nephrons in kidney. It is called diuresis. It reduces the loss of water. When the ADH is less secreted it.leads to the excess loss of water and dehydration occurs. The kidney is unable to conserve water. This disorder is called diabetes insipidus.
