Functions of Endocrine Glands or their Hormones
By – Prof.Dr.R.R.deshpande ( MD in Chikitsa & Kriya )
Article is from his own Text Book of Kriya Sharir Paper 1 Part A & Part B
1) Pituitary Gland
The pituitary gland secretes a variety of different hormones. They are -
1) Growth hormone - which controls growth.
2) Prolactin - which promote milk production at the end of pregnancy.
3) Thyroid - Stimulating hormone which control the output of thyroid hormone (TSH).
4) Follicle - Stimulating hormone (FSH) & luteinizing hormone (LH), which control the production of eggs (Ovum) from the ovary & maintenance of pregnancy after fertilization 5) Adrenocorticotropic hormone (ACTH) - which control the output of cortisol from the adrenal glands.
6) Oxytocin - which releases milk from the breast & causes the womb (Uterus) to contract.
7) Vasopressin - Also called the antidiuretic hormone, which increases the reabsorption of water in the kidneys & controls water loss.
8) Melanocyte Stimulating hormone (MSH), which stimulates the growth of pigment cells in the skin.
1) Growth Hormone (G.H.)
Secreted by chromophils (Acidophilic cells)
G.H. = Somatotrophic Hormone (S.T.H.) (Soma = body cell)
The function of this hormone is seen on all the cells of the body, except reproductive cells.
i) Promotes & regulates the process of growth.
ii) Increase of Messenger RNA in the cells, which promotes protein synthesis.
iii) Amino acid transport & protein synthesis is enhanced.
iv) Accelerate linear growth of skeleton & widening of epiphysis.
Muscles, viscera & tissue increase in size & weight.
v) Rate of carbohydrate utilization decreases. So conservation process takes place.
vi) Fat metabolism increases blood level of free fatty acids & glycerol increases.
vii) Increased retention of sodium, potassium & phosphorus
Causes of excessive GH - Tumour, idiopathic (cause not known)
A) Hyper secretion of GH
1) Gigantism - It occurs in the growing age (12 to 20 years)
i) Overgrowth of skeleton (Height becomes 7 to 8 feet). Bones are thickened & deformed.
ii) Increase in the size of muscles, viscera & other body tissues.
iii) Skin & subcutaneous tissue – thick. iv) BMR increases
If GH secretion increases, in the adult person then in spite of linear growth, transverse growth occurs
i) Enlargement, overgrowth & thickening of bones of limbs, jaw, cheeks & supra orbital ridges. ii) Skull bones thickened.
iii) Face appears broader. iv) Hands & feet thickened.
v) Viscera (Heart, lungs, liver & spleen) enlarged.
B) Hyposecretion of GH
Causes - Necrosis of the gland, after intracranial hemorrhage
a) Lorain levy type
i) Stunted body growth up to the 3 feet
ii) Sex organs remain infantile
iii) Metabolic functions & intelligence can remain normal.
a) Brissaud type
Symptoms - i) Symptoms are same as above.
ii) In addition, excessive fat deposition on face.
If growth hormone is absent during early life, pituitary Dwarfism results. Excess during this period causes Gigantism. After the end of the growth period, excess growth hormone causes the disease Acromegaly. Pituitary failure has widespread effects, including failure of normal sexual development at puberty, loss of steroid (Cortisol) production & consequent weakness, a low metabolic rate from thyroid under action, an excessive urinary output (Diuresis) & bleaching of the skin.
Cushing's Syndrome is a result of excessive output of some of the pituitary hormones, usually from a tumour. Simmond's disease is the result of extreme under function of the gland, usually from loss of blood supply / destruction by tumour. The effect is severe weight loss, great weakness & under activity of the thyroid & adrenal glands. Diabetes insipidus is the result of lack of production of the hormone vasopressin. There is an abnormally large output of urine, resulting in extreme thirst. Deficiency of this hormone causes the tubules of the kidneys to lose their power to concentrate urine.
The other endocrine glands
Prompted by the pituitary, the other endocrine gland, in turn, produce their own hormones such as -
1) Adrenaline - From the inner part of the adrenal glands.
2) Cortisol (Corticosteroid) - From the outer part of the adrenals.
3) Thyroxine, Tri - iodothyronine - From the thyroid gland.
4) Calcitonin - From the thyroid gland.
5) Insulin & Glucagon - From the pancreas.
6) Parathyroid - From the parathyroid gland
7) Oestrogen & Progesterone - From the ovaries.
8) Testosterone - From the testicles
Functions of Thyroid Glands
1) Convert energy into heat
(by oxidative phosphorylation – ATP break down)
Body temperature is maintained by this heat.
40% heat produced in the body is regulated by thyroid gland. So, in the thyroid deficiency BMR is reduced.
2) Tissue & cellular metabolism is stimulated
3) Metabolism of Nutrients
Protein – Uptake & break down of proteins is accelerated
Carbohydrates – More breakdown of carbohydrates. Hence, in hyperthyroidism, mild diabetic symptoms are observed.
Fats – Blood cholesterol level goes down (Normal cholesterol level in the blood is equal to 200 mg%. in hyperthyroidism cholesterol level can be up to 120-100 mg %)
Minerals – Calcium & phosphates are removed from bones & excreted in more mount.
In thyroid deficiency. NaCl is retained in ECF (Extra Cellular Fluid) So, increased fluid retention & oedema a develops in Myxoedema.
Vitamins – Thyroxine helps in conversion of β carotene into vitamin A.
4) Effects on various organs
i) CNS – Due to deficiency of thyroxine, subnormal development of Neurons (Hence, mental retardation is seen in cretinism )
ii) CVS (Cardio Vascular System) – Due to more O2 consumption rate & force of cardiac output increases. (Hence in hyper thyroidism, patient complains of (c/o) Tachycardia. Palpitation (Perceiving the self heart sound)
iii) G.I. tract (Gastrointestinal tract) – Thyroxin increases the absorption rate & hence appetite increases.
iv) Bone – Removal of calcium & phosphorus from bones (In hyper secretions due to Demineralization bones become hollow & osteoporosis develops)
v) Testes & ovaries – Normal functioning of gonads.
vi) Blood – Normal maturation of RBC’ s
vii) Mammary glands – Maintain & increased secretion of Milk (Lactation)
5) Thyroid hormone is essential for normal metabolic processes. So, normal body development is also depends on this hormone. Hence in thyroid deficiency (Cretinism) retarted growth is seen.
6) Thyroid Hormone maintains body temperature.
7) Thyroid hormone maintains water balance in the body (by controlling ECF – Extra cellular fluid)
3) Parathyroid Glands
These are 4 small, bean - shaped organs, each about half a centimeter long, which lie in the substance of the thyroid Gland. They secrete the hormone called Parathormone, which regulates the fate of calcium & phosphorous in the body. This hormone is automatically produced, if the level of calcium in the blood drops & its presence causes the blood calcium level to rise again by the release of calcium from the bones, a reduction in calcium loss by the kidneys & increased absorption from the bowel.
Sometimes the Parathyroids enlarge / develop tumours & secrete too much parathormone. The result is excessive loss of calcium from bones resulting in softening. Surgery is usually necessary to remove some of the glands. Insufficient parathormone result in low blood calcium - a potentially dangerous condition featuring abnormal muscles excitability & spasm (Tetany).
4) The adrenal glands
The adrenals are 2 small but important endocrine organs, sitting like triangular caps - one on the top of each kidney. Each adrenal has 2 distinct parts, the inner core - which produces adrenaline & an outer layer (Cortex) - which produces 3 kinds of steroid hormones - Cortisol to help the body to react to stress, Aldosterone to control water balance & sex hormones. Because all these hormones have such a powerful effect on the body, any disorder of the adrenals is serious.
Adrenaline is the secretion of the inner part of the adrenal glands & of certain nerve endings. It is produced when the body is required to make unusual efforts. It speeds up the heart, increases the rate breathing, raises the blood pressure, deflects the blood circulation from the digestive system to the muscles, mobilizes the fuel glucose & causes a sense of alertness & excitement. These changes allow more effective physical action, as may be needed in a situation of danger. It has been described as the hormone of 'fright, fight / flight'. One of the ways in which stress is thought to cause damage is by the over - frequent & inappropriate production of adrenaline & the resultant raising of the blood pressure with possible permanent damage to the vital arteries.
The natural corticosteroid hormones secreted by the cortex of the adrenal glands are cortisol, corticosterone, aldosterone & androsterone. Cortisol & corticosterone are called glucocorticoids because they are concerned with the body's usage of glucose & other nutrients. Aldosterone is called as mineral corticoid because it is responsible for the control of blood levels of minerals such as sodium & potassium and, thereby, control of water balance. Androsterone is an androgen, a male sex hormone similar to testosterone produced in the testicles.
Details of Glucocorticoids
1) Hypersensitivity due to allergy is inhibited. Histamine synthesis depressed. Check anaphylactic shock (inj. Decadron / Efcorlin should be in the emergency bag.)
2) Produce peripheral vasoconstriction, hence BP rises. This function is useful in the hypotensive shock.
3) Eosinophil count is reduced hence used in the condition of Eosinophilia (Causes are – Bronchial asthma, allergy worms, Tropical eosinophilia)
4) Muscular action is stimulated, hence used in bodyache & backache.
5) Counter act the symptoms of stress.
6) Mental changes – Euphoria (Mental feeling of enjoyment)
7) Promote the secretion of HCl in the stomach. Hence steroids should not be used in the cases of hyperacidity / peptic ulcer
8) Anti-inflammatory action – used in R.A. (Rheumatoid arthritis)
9) Action on nutrients
a) Proteins – Steroids break down the tissue proteins.
b) Due to steroids, blood sugar level increases (Hence contraindicated in diabetes mellitus)
c) Fats – Steroids increase the absorption of dietary fat (Hence uncontrolled use of steroids may increase the obesity)
Details of Adrenaline (Epinephrine)
Actions of Adrenaline
1) Systolic blood pressure is raised.
2) Rate, force & output of the heart is increased.
3) Coronary blood vessels are dilated.
4) Eyes – pupils are dilated.
5) Skeletal muscles are stimulated, enhanced working capacity, hence delayed fatigue.
6) Smooth muscles of G.I. tract, urinary bladder & uterus are relaxed.
7) BMR is increased, blood glucose level is increased.
Note - Inj. Adrenaline subcutaneous (S/C) is also a life saving drug & should be kept in emergency bag.
Adrenaline acts as a neurotransmitter at the sympathetic system.
Details of Nor-Adrenaline (Nor-Epinephrine)
Actions of Non-adrenaline
1) General vasoconstrictor.
2) Hence systolic & diastolic both the types of blood pressure are raised.
3) Pathology - Over secretion of nor-adrenaline
Cause - Benign tumour of adrenal medulla (Pheocromocytoma)
Investigation - Urinary catecholamines (VMA) are increased in 24 hr. urine sample.
5) The pancreas
The pancreas produces digestive enzymes which pass into the first part of the small intestine (Duodenum). But it is also an endocrine gland, containing groups of specialized cells, in areas known as the Islets of Langerhans, which monitor the concentration of glucose in the blood & secrete appropriate amount of the hormones, insulin & glucagon to lower / raise the amounts of sugar as necessary.
Glucagon is a protein hormone, produced by the islet cells of the gland, which has an effect opposite to that of insulin. Glucagon is also involved in the mobilization of fatty acids for energy purposes. It is used as an emergency measure when the blood sugar levels are dangerously low (Hypo glycaemia) & must be rapidly raised. A glucagon injection can prevent brain damage / even save life.
Insulin acts by forming port on cell membranes which allows glucose to pass in. In its absence, glucose, which is the main fuel of the body, can not get into the cells & accumulates in the blood. The body responds to its need for glucose by releasing more from the muscles which waste away. The wasting disorder caused by insufficient insulin is called Diabetes mellitus & is corrected by injections of insulin.
Functions of Testesteron
1) Development & maintains male accessory organs (like seminal vesicles, prostate gland)
2) Enhances spermatogenesis
3) Development & control of secondary sex characters in male.
4) Acts as an anabolic hormone in association with GH.
Affecting protein metabolism – Positive nitrogen balance
Deposition of calcium in bones & their development
Na, K, Ca, P – These minerals are retained in the body
Stimulates growth & body weight increases.
5) Stimulation of Erythropoiesis
6) BMR is increased.
7) Skin – Subcutaneous tissue, sweat & sebaceous gland are developed & they are under the influence of testesterone.
8) Renal blood flow increases.
9) Development of emotional maturity.
Functions of Oestrogen
1) Development of female accessory sex organs.
2) Development of female secondary sex characters.
3) Menstrual cycle – Oestrogen influences Follicular phase i.e. 1st half of menstrual cycle. Oestrogen secretion is maximum around ovulation period. During secretory phase (2nd half of M.C.) Oestrogen acts with progesterone.
4) During pregnancy – Oestrogen secretion by placenta keeps on increasing till full term, when myometrium of uterus develops under its action.
5) Vaginal epithelium multiplies & is keratinized by oestrogen & pH of vaginal secretion becomes more acidic (prevents infection)
6) Due to oestrogen, calcium deposition in the bones in stimulated.
Hence Osteoporosis / backache are common problems after menopause. In these cases gynecologist suggest HRT (Hormonal Replacement Therapy)
7) Oestrogen prevents atherosclerotic changes. Hence, after menopause, hypertension is common in the females also.
Functions of Progesterone
Secreted by Corpus luteum & by placenta.
1) Progesterone with oestrogen maintains the secretory phase of menstrual cycle.
Withdrawal bleeding is due to fall in progesterone level.
2) Progesterone helps in embedding of fertilizing ovum & its nourishment.
3) Progesterone influences, the formation of placenta. After 1st Trimester, placenta secretes progesterone.
4) Progesterone serves to make the myometrium of gravid uterus, which is non-sensitive to the action of Oxytocin. Action of Oxytocin starts at the time of parturition (labour)
5) Progesterone influences the development of mammary gland (only the growth but not the milk production)
6) Due to progesterone, birth canal, during pregnancy is enlarged.
7) During the progesterone therapy, development & rupture of Graffian follicle is inhibited resulting unovulatory menstrual cycle.
7) Thymus gland
1) Thymus gland is partly lymphoid & partly endocrine in function.
2) Thymus gland is one of the seats of lymphocyte formation in children.
3) Thymus gland has a relation with the growth of gonads.
4) Thymus helps for the salt deposition in the bones.
5) Recently, it is found that thymus is important in association with immunological processes in the body.
6) Small lymphocytes are said to migrate to various antibody-forming tissues of the body (Spleen, lymph node, thymus etc.)
7) Thymus gland produces ‘curare-like substance which depresses Myoneural junction. Hence, in the disease ‘Myasthenia Gravis’, thymus is found to be enlarged. Myasthenia Gravis is a disease due to deficiency of Ach i.e. Acetylcholine.