What is Thyroxine?
Thyroxine, also known as T4, is the main hormone which is secreted by the thyroid gland into the bloodstream. Although it is an inactive form, most of it is converted to an active form called triiodothyronine by organs such as the liver and kidneys. The hypothalamus in the brain along with the pituitary and thyroid glands modulate the production and release of thyroid hormones.
What Happens If You Have Too Little Thyroxine?
If the level of thyroxine in the blood is low, then the pituitary gland releases more thyroid-stimulating hormone (TSH) to try and stimulate the thyroid gland to make more thyroxine. Therefore, a raised level of TSH means the thyroid gland is underactive and is not making enough thyroxine. When the thyroid gland produces very little quantity of thyroxine, then the condition is known as hypothyroidism.
As thyroid hormones are essential for physical and mental development, so hypothyroidism during development or before birth and during childhood causes mental impairment and reduced physical growth.
Symptoms usually show a slow and gradual progression before they become worse over months or years as the level of thyroxine in the body gradually falls.
In adults it causes a decrease in metabolic rate resulting in symptoms that include:
Less Common Symptoms include:
Diagnosis and Investigations:
It involves a blood test which screens the levels of TSH and free T4 and T3. Usually, the reports show high TSH and T3 and T4 levels.
Treatment usually involves taking a daily tablet of thyroid hormone levothyroxine to replace the missing thyroxine. Treatment works very well for most people with hypothyroidism but is required for life.