Thyroid hormone – Synthesis and functions

Often you will tend to hear about thyroid hormone very much correlated with the body function. Whenever you get deviated from the regular activities, the foremost questions arise will be like check your thyroid, what js your T3 and T4 levels ?? Rite !!!! So why these hormone have special concern? What are their functions and how their imbalance will impact our body ? Let’s have a look…

Secretions of thyroid hormone :

Thyroid hormone secretes,

Synthesis of thyroid hormone is controlled by thyroid stimulating hormone (TSH) from anterior pituitary gland and iodine is the key element required for the synthesis of T3 and T4.

Functions of T3 and T4 :

Functions of thyroid hormone on specific bodily mechanisms:

  • Stimulate carbohydrate metabolism
  • stimulate fat metabolism
  • Increased requirement of vitamins
  • maintain basal metabolic rate (BMR)

All these factors will help to maintain tan the body weight under control.

Functions of thyroid hormone on heart and blood vessels:

  • Increased blood flow and cardiac output
  • Maintain the heart rate
  • strengthen the heart
  • Maintain the blood pressure mainly on the arteries.

Functions on respiration :

Increase the rate and depth of respiration thereby increasing the oxygen consumption of the body

Functions on gastrointestinal tract:

  • Increase appetite and food intake
  • increase digestive juice secretion
  • Increase intestinal motility and provide effective digestive process

Functions on muscles and nervous system :

In general thyroid hormone increase the rapidity of cerebral function and also helpful for maintaining the proper sleep cycle. Thyroid hormone plays an essential role for body builders.

Functions on other hormones :

For normal sexual functions, thyroid hormone needs to be approximately normal. Thyroid hormone indirectly regulate the function of other hormones like insulin, glucagon, growth hormone and corticosteroids.

Functions of calcitonin :

  • Increase the bone density by increasing the calcium deposits on the bone
  • Decrease the blood calcium level
  • Decrease the osteoclastic (bone destructive cell) activity

* The role of thyroid hormone on the calcium regulation is of significantly less importance as compared to the parathyroid hormone.

Any imbalance in the secretion of thyroid hormone will cause either hyperthyroidism (increased secretion ) or hypothyroidism ( decreased secretion) which will have their own consequences attributed to the above functions.Signs and symptoms of hyperthyroidism and hypothyroidism

 

References :

Textbook of medical physiology by Arthur C.Guyton

Ganong’s review of medical physiology

 

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