HYPOTHYROIDISM

HYPOTHYROIDISM

The condition of the thyroid gland, wherein it fails to produce adequate amounts of thyroid hormone for the body. This is a fairly common disorder, being more prevalent in females.

Firstly, we’ll learn about the normal functioning of the thyroid gland.

It is a butterfly shaped gland which functions under regulation of the anterior pituitary and hypothalamus.

As is clear from the image, the hypothalamus produces TRH( thyroid releasing hormone) which acts on our master gland i.e pituitary and stimulates it to produces TSH( thyroid stimulating hormone). TSH then acts on the thyroid gland and causes release of our well known thyroid hormones –T3 and T4. 

In order to prevent excess of thyroid hormones to circulate in the body, the thyroid hormones themselves put a stop on the pituitary and hypothalamus. Thus the higher order hormones (TSH and  TRH) are kept in control by our body’s innate mechanisms.

Normal thyroid hormone levels in the body:

Though the levels of serum T4 is higher compared to serum T3, the active form of thyroid hormone is T3.

What role do the thyroid hormones have?

It plays a major role in the metabolism, growth and development of the human body. Many body functions are regulated by the constant release of a steady amount of thyroid hormones into the bloodstream. If the body needs more energy in certain situations – for instance, if it is growing , or exposure to cold, or during pregnancy , more of the hormone is secreted.

A defect anywhere in the hypothalamo-pituitary-thyroid axis can cause hypothyroidism.

The causes can be primary or secondary.  

PRIMARY CAUSES	SECONDARY CAUSES
Those causes that affect the thyroid gland directly. For eg.: ·        Congenital defects in thyroid development. ·        Surgery ·        Radioactive therapy /external radiations. ·        Autoimmune – Hashimoto’s thyroiditis. ·        Iodine deficiencies ·        Drugs (like lithium, iodides, p-aminosalicylic acid)	Those that affect our higher(central) hormones. These are generally rare. For eg.:          Pituitary failure          Hypothalamic failure

PRIMARY CAUSES

SECONDARY CAUSES

Those causes that affect the thyroid gland directly.

For eg.:

·        Congenital defects in thyroid development.

·        Surgery

·        Radioactive therapy /external radiations.

·        Autoimmune – Hashimoto’s thyroiditis.

·        Iodine deficiencies

·        Drugs (like lithium, iodides,

p-aminosalicylic acid)

Those that affect our higher(central) hormones.

These are generally rare.

For eg.:

         Pituitary failure

         Hypothalamic failure

Note : Treatment for hyperthyroidism [excessof thyroid hormones] can (in some cases) lead to hypothyroidism. Also, after surgically resecting the thyroid gland in cases of cancer or treatment of hyperthyroidism, there are high chances that the patient may have hypothyroidism.  

A decrease in thyroid hormone levels will cause disregulation of the central hormones; There will no longer be an inhibitory force. Excess of TRH and TSH will lead to enlargment of the thyroid gland, more commonly referred to as -Goitre.

 As the major function of thyroid hormones is to maintain body metabolisms, any decrease in their levels will lead to the following symptoms:

•         Fatigue
•         Weakness
•         Muscle cramps
•         Constipation
•         Intolerance to cold
•         Weight gain
•         Poor appetite
•         Enlargement of thyroid gland- Goitre

Any such symptoms should be reported to the doctor. On the basis of your thyroid function test results, preferred treatment is to be given.