12th Zoology

Pituitary gland hormone

Pituitary gland

The Pituitary gland is otherwise called the hypophysis. It is located at
the base of the brain. It is approximately 1 cm long, 1-1.5 cm wide and 0.5 cm thick. It weighs about 500 mg. Anatomically the pituitary gland is divisible
into anterior adenohypophysis and posterior neurohypophysis.

The adenohypophysis consists of three lobes or zones namely, Pars intermedia,
Pars distalis and Pars tuberalis. The anterior lobe or adenohypophysis is
embryologically derived from the roof of the mouth as a dorsal pouch. The
neurohypophysis on the other hand, originates from the floor of
diencephalon, as a downward growth.

The hormones of anterior pituitary

The adenohypophysis is responsible for the secretion of six trophic
hormones or tropins. They are growth hormone or somatotropic
hormone (GH/STH), thyrotropic hormone or thyroid stimulating
hormone (TSH), Adrenocortico tropic hormone (ACTH), Follicle
Stimulating Hormone (FSH), Leutinizing hormone (LH) and Prolactin
or Leuteotropic hormone (LTH). (Pituitary gland)

Metabolic functions of the growth hormone

Growth hormone is responsible for various general metabolic
functions. It affects the diverse spectrum of integrated metabolic reactions,
which participate in the overall process of growth. Growth hormone
influences carbohydrate, protein and lipid metabolism.

Growth hormone stimulates both the formation of cartilage (Chondrogenesis) as well as bone (Osteogenesis). It causes the retention of minerals such as nitrogen,
potassium, phosphorus, sodium, etc useful for growth.

Deficiency of growth hormone or hyposecretion in children results in
retarded growth. The premature arrest of skeletal development causes
dwarfism. The adult dwarfs will grow to a height of only 0.9 to 1.2 meter.

They never attain puberty or do not develop secondary sexual characters.
Excessive secretion of GH results in over growth of the skeletal
structures and the person may reach a height of 7 to 9 feet
(gigantism).

The excessive GH in adults also results in the increase in thickness of lower jaw and disproportionate over growth of bones of the face, hands and feet. The above condition is known as acromegaly. (Pituitary gland)

Thyrotrophic hormone or thyroid stimulating hormone (TSH)

TSH is a glycoprotein with a molecular weight of 28,000 daltons. It
is made up of 211 amino acids. The specific target organ for the TSH is the
thyroid gland. It stimulates the thyroid to secrete the thyroxine.

There exists a negative feedback mechanism between the circulating level of thyroxine and the hypothalamic releasing factor. When the thyroxione is less in blood, the hypothalamus produces more TSH releasing factor which on reaching
the pituitary stimulates secretion of TSH. TSH on reaching the thyroid,
stimulates the thyroid to secrete more hormone.

Conversely, when there is excess thyroxine in the blood, the production of thyroxine is controlled by non-secretion of releasing factor from the hypothalamus. (Pituitary gland)

Adreno cortico trophic hormone (ACTH)

It is a protein hormone. ACTH also functions by the negative feed
back mechanism and stimulates the adrenal cortex and its secretion. Its other functions include the stimulation of formation of melanin pigments in the
melanocytes of the skin, stimulation of insulin secretion and mobilization of
fats from adipose tissue.

Follicle stimulating hormone (FSH)

It is a gonadotropic hormone that directly stimulates the gonadal functions
in both males and females. The human FSH is a small glyco
protein.

The target organs for FSH in the females are the ovaries. It
promotes the growth of graffian follicles and thereby increases the total weight
of the ovary. It also promotes the secretion of oestrogen.

In males, the target organs for FSH are the testes. It directly stimulates the germinal epithelium of the seminiferous tubules and augment the rate of spermatogenesis. (Pituitary gland)

Leutinizing hormone or Interstitial cells stimulating hormone (LH or
ICSH)

Human ICSH or LH is a glycoprotein. In females, the LH stimulates
the ripening of ovarian follicles and induces ovulation. In males, the LH or
ICSH, specifically affects the leydig cells or interstitial cells of the testes and
stimulates the synthesis and secretion of the male hormone (Androgen)
testosterone.

Prolactin or Luteotropic hormone (LTH)

Prolactin is called by several names such as luteotropin, luteotrophic
hormone, lactogenic hormone, mammotropin etc. It is a protein hormone. Its
main function is stimulation of milk formation or initiation of lactation
following parturition in mammals.

It also stimulates the corpus luteum to secrete the progesterone. Prolactin together with estrogen stimulates the growth of mammary glands and makes it ready for milk secretion. (Pituitary gland)

Related Topics in Zoology:

Bio Zoology All Important Topics


  1. Human Physiology Introduction

  2. Nutrition

  3. Carbohydrates Poly hydroxyaldehydes (or) ketones

  4. Proteins (Polypeptides)

  5. Lipids

  6. Vitamins – Functions Of Vitamins

  7. Deficiency of Vitamin

  8. Minerals – Water – Role of water

  9. Balanced diet

  10. Obesity

  11. Digestive System

  12. Dental Caries (Tooth decay)

  13. Root Canal Treatment

  14. Peptic ulcer

  15. Hernia and Types

  16. Appendicitis (Appendix)

  17. Gall Stones

  18. Hepatitis

  19. Fractures – Types of fractures

  20. Mechanism of fracture

  21. Dislocation of joints

  22. Arthiritis

  23. Rickets and Osteomalacia – Orthopedics

  24. Muscles

  25. Mechanism of muscle contraction

  26. Types of muscle contraction

  27. Myasthenia Gravis

  28. Respiration – Process of pulmonary respiration

  29. Mechanism of Breathing

  30. Regulation of Respiration

  31. Pneumonia Tuberculosis Symptoms Treatment

  32. Bronchitis – Acute bronchitis, Chronic Bronchitis Causes

  33. Circulatory System – Functioning of Human heart

  34. Cardiac Cycle

  35. Coronary blood vessel and its significance

  36. Myocardial infarction

  37. Angina pectoris

  38. Angiogram – Angioplasty

  39. Atherosclerosis

  40. Heart block Echo cardiography Heart Valves

  41. Rheumatic Heart Disease (RHD), ICCU – (Intensive Coronary Care Unit)

  42. Blood Pressure

  43. Heart transplantation

  44. Pulse rate

  45. Cardio Pulmonary Resuscitation (CPR)

  46. Blood – Composition of plasma – Blood cells

  47. Clotting of Blood or Haemostasis

  48. Thrombosis

  49. Nervous system Co-ordination systems

  50. The Brain – Fore Brain, Midbrain, Hindbrain

  51. Memory

  52. Sleep – Types of sleep

  53. Stroke – Brain haemorrhage

  54. Alzheimer – Meningitis (Brain fever)

  55. Conditioned reflex

  56. Electroencephalography EEG

  57. Right and Left brain concept

  58. Spinal cord functioning

  59. Chemical co-ordination – Functions of Endocrine glands

  60. Hypothalamus

  61. Pituitary gland – hormone

  62. Hormones of Neurohypophysis – vasopressin

  63. Thyroid gland

  64. Parathyroid Gland

  65. Pancreas

  66. Adrenal gland

  67. Gonads

  68. Receptor Organs – Eye

  69. Photochemistry of Retinal visual Pigments

  70. Errors of refraction

  71. Optometry – Retinopathy

  72. Cataract – Lens Replacement – Glaucoma – Nyctalopia

  73. Eye Infections and Eye Care

  74. Ear

  75. Mechanism of hearing

  76. Defects of the ear

  77. Hearing Aid – Noise pollution

  78. Skin and functions of skin

  79. Melanin functions

  80. Effects of solar radiation / UV radiation – Skin grafting

  81. Dermatitis

  82. Tongue – Mechanism of Stimulation

  83. Excretion Ureotelism Nephron

  84. Mechanism of urine formation

  85. Renal Failure, Dialysis, Kidney Machines

  86. Kidney stone – Kidney transplantation

  87. Diabetes mellitus

  88. Functioning of male reproductive system

  89. Functioning of female reproductive system

  90. Ovulation and fate of the ovum – Menstrual cycle

  91. Fertilization

  92. Birth control

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