Thyroid gland , Diseases of thyroid gland & Function of Parathyroid glands

Thyroid gland

Thyroid gland lies in the anterior part of neck and in a close contact with the trachea , Its colour is slightly red , It is surrounded by a membrane of connective tissue , It consists of two lobes that are connected together by an isthmus , the thyroid gland secretes two important hormones which are thyroxine hormone and calcitonin hormone .

Thyroxine hormone ( iodine element is essential for its formation ) that has many effects on different parts of the body such as :

  • It affects and stimulates the physical and mental growth .
  • It affects and controls the main metabolic rate .
  • It increases the absorbtion of carbohydrates ( monosacchrides ) from the intestine .
  • It maintains the skin and hair healthy .

Calcitonin hormone which decreases the calcium level in the blood and it prevents the withdrawal of calcium from the bones .

Diseases of thyroid gland : The diseases are caused due to the increase or decrease in the secretion of thyroxine hormone such as goiter and there are two types of this diseases which are :

  • Simple goiter which arises due to the hyposecretion of thyroxine hormone .
  • Exophthalmic goiter which arises due to the hypersecretion of thyroxine hormone .


Causes : hyposecretion of thyroxine hormone , due to the deficiency of iodine in food , water and air .

Treatment : addition of iodine to salt and different food .

Complications that result from the severe hyposecretion of thyroxine hormone :


Causes : acute hyposecretion of thyroxine hormone during childhood .

Symptoms :

  • Physical growth : large head , short stature and short neck .
  • Mental growth : it may cause a permanent mental retardation .
  • Sexual maturity : it may cause a delay in the sexual maturity .

Causes : acute hyposecretion of thyroxine hormone in adults .

Symptoms :

  • Skin dryness and loss of hair .
  • Weight gain and obesity .
  • Decreasing the main metabolic rate that causes cold intolerance .
  • Decreasing the heartbeats and rapid fatigability .

Treatment : by using thyroid gland hormones or its extracts under the supervision and regular consultation of a specialist .


Exophthalmic goiter

Causes : hypersecretion of thyroxine hormone .

Symptoms :

  • Noticed enlargement of the thyroid gland and anterior part of the neck with protrusion of the eye balls .
  • Increase in the food oxidation and metabolic rate .
  • Increase in the heartbeats .
  • Loss of weight and nervous irritability .

Treatment is either by surgical removal of a part of the thyroid gland or using other medications to suppress the gland .

Thyroid gland and Parathyroid glands

Thyroid gland and Parathyroid glands

Parathyroid glands  

It consists of four small separate lobes , where each two of them are located on each side of the thyroid gland and it secretes parathormone hormone :

Function of parathormone hormone :

  • It plays an important role with calcitonin hormone ( secreted from thyroid gland ) in preserving the normal calcium level in blood .
  • Amount of parathormone hormone depends on the calcium level in the blood , where its secretion increases , when the calcium level in blood decreases .

Hypersecretion of parathormone hormone ( Hyperparathyroidism ) leads to increasing the calcium level in the blood , as most of the calcium is released from the bones which leads to bone resorption and the bones become fragile and liable for bending and fracture .

Hyposecretion of parathormone hormone ( Hypoparathyroidism ) leads to :

  • Decreasing the calcium level in the blood .
  • Painful convulsions and muscle spasm .
  • Increasing the excitability of nervous system .

Endocrine system , Endocrine glands , Pituitary gland & Hormonal coordination in living organisms

Adrenal ( suprarenal ) glands , Pancreas & Sex glands ( Gonads )

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