Explain the following Human Endocrine Glands 1. Pituitary gland 2. Thyroid gland 3. Parathyroid gland

Pituitary Gland

  • The pituitary gland or hypophysis is a pea-shaped compact mass of cells located at the base of the midbrain attached to the hypothalamus by a pituitary stalk. 
  • The pituitary gland is anatomically composed of two lobes and performs different functions. 
  • They are the anterior lobe (adenohypophysis) and the posterior lobe (neurohypophysis). The intermediate lobe is non-existent in humans.
  • The pituitary gland forms the major endocrine gland in most vertebrates. It regulates and controls other endocrine glands and so is called as the “Master gland”.
  • Hormones secreted by the anterior lobe (Adenohypophysis) of pituitary
  • The anterior pituitary is composed of different types of cells and secretes hormones which stimulate the production of hormones by other endocrine glands. 
  • The hormones secreted by the anterior pituitary are
    • Growth Hormone
    • Thyroid stimulating Hormone
    • Adrenocorticotropic Hormone
  • Gonadotropic Hormone which comprises the Follicle Stimulating Hormone and Luteinizing Hormone

Growth hormone (GH)

  • GH promotes the development and enlargement of all tissues of the body. 
  • It stimulates the growth of muscles, cartilage and long bones. It controls cell metabolism.
  • The improper secretion of this hormone leads to the following conditions.


  • It is caused by decreased secretion of growth hormone in children. The characteristic features are stunted growth, delayed skeletal formation and mental disability.


  • Over secretion of growth hormone leads to gigantism in children. 
  • It is characterised by the overgrowth of all body tissues and organs. Individuals attain an abnormal increase in height.


  • Excess secretion of growth hormone in adults may lead to abnormal enlargement of the head, face, hands and feet.

Thyroid-stimulating hormone (TSH)

  • TSH controls the growth of the thyroid gland and coordinates its activities and hormone secretion.

Adrenocorticotropic hormone (ACTH)

  • ACTH stimulates the adrenal cortex of the adrenal gland for the production of its hormones. It also influences protein synthesis in the adrenal cortex.

 Gonadotropic hormones (GTH)

  • The gonadotropic hormones are follicle stimulating hormone and luteinizing hormone which are essential for the normal development of gonads.

Follicle-stimulating hormone (FSH)

  • In males, it stimulates the germinal epithelium of testes for the formation of sperms. 
  • In females, it initiates the growth of ovarian follicles and their development in the ovary.

Luteinizing hormone (LH)

  • In males, it promotes the Leydig cells of the testes to secrete the male sex hormone testosterone. 
  • In females, it causes ovulation (rupture of mature Graafian follicle), responsible for the development of corpus luteum and production of female sex hormones estrogen and progesterone.

Prolactin (PRL)

  • PRL is also called lactogenic hormone. 
  • This hormone initiates the development of mammary glands during pregnancy and stimulates the production of milk after childbirth.
  • Hormones secreted by the posterior lobe (Neurohypophysis) of pituitary
  • The hormones secreted by the posterior pituitary are
    • Vasopressin or Antidiuretic hormone
    • Oxytocin

Vasopressin or Antidiuretic hormone (ADH)

  • In kidney tubules, it increases the reabsorption of water. 
  • It reduces the loss of water through urine and hence the name antidiuretic hormone.
  • The deficiency of ADH reduces the reabsorption of water and causes an increase in urine output (polyuria). This deficiency disorder is called Diabetes insipidus.


  • It helps in the contraction of the smooth muscles of the uterus at the time of childbirth and milk ejection from the mammary gland after childbirth.


  • Melatonin is a hormone produced by the pineal gland. It is known as a time messenger. It signals nighttime information throughout the body.
  • Exposure to light at night, especially short-wavelength light, can decrease melatonin production interrupting sleep. 
  • Suppression of melatonin has been implicated in sleep disturbances and related metabolic disorders.

Thyroid Gland

  • The thyroid gland is composed of two distinct lobes lying on either side of the trachea. 
  • The two lobes are connected by means of a narrow band of tissue known as the isthmus. 
  • This gland is composed of glandular follicles and lined by cuboidal epithelium. 
  • The follicles are filled with colloid material called thyroglobulin.
  • An amino acid tyrosine and iodine are involved in the formation of thyroid hormone. 
  • The hormones secreted by the thyroid gland are
    • Triiodothyronine (T,)
    • Tetraiodothyronine or Thyroxine (T)

Functions of thyroid hormones

  • Production of energy by maintaining the
  • Basal Metabolic Rate (BMR) of the body.
  • Helps to maintain normal body temperature.
  • Influences the activity of the central nervous system.
  • Controls growth of the body and bone formation.
  • Essential for normal physical, mental and personality development.
  • It is also known as the personality hormone.
  • Regulates cell metabolism.

Thyroid Dysfunction

  • When the thyroid gland fails to secrete the normal level of hormones, the condition is called thyroid dysfunction. It leads to the following conditions


  • It is caused due to the decreased secretion of thyroid hormones. The abnormal conditions are simple goitre, cretinism and myxoedema.


  • It is caused due to the inadequate supply of iodine in our diet. 
  • This is commonly prevalent in Himalayan regions due to the low levels of iodine content in the soil. 
  • It leads to the enlargement of the thyroid gland which protrudes as a marked swelling in the neck and is called a goitre.


  • It is caused due to decreased secretion of the thyroid hormones in children. 
  • The conditions are stunted growth, mental defect, lack of skeletal development and deformed bones. They are called as cretins.


  • It is caused by deficiency of thyroid hormones in adults. 
  • They are mentally sluggish, increase in body weight, puffiness of the face and hand, oedematous appearance.


  • It is caused due to the excess secretion of the thyroid hormones which leads to Grave’s disease. 
  • The symptoms are protrusion of the eyeballs (Exopthalmia), increased metabolic rate, high body temperature, profuse sweating, loss of body weight and nervousness.

Parathyroid Gland

  • The parathyroid glands are four small oval bodies that are situated on the posterior surface of the thyroid lobes. 
  • The chief cells of the gland are mainly concerned with secretion of parathormone.

Functions of Parathormone

  • The parathormone regulates calcium and phosphorus metabolism in the body. 
  • They act on bone, kidney and intestine to maintain blood calcium levels.

Parthyroid Dysfunction

  • The secretion of parathyroid hormone can be altered due to the following conditions.
  • Removal of parathyroid glands during thyroidectomy (removal of thyroid) causes decreased secretion of parathormone. 

The conditions are

  • Muscle spasm known as Tetany (sustained contraction of muscles in face, larynx, hands and feet).
  • Painful cramps of the limb muscles.
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