Pharmacology Teaching and Research

Online Lecture: Endocrine System

Drugs Affecting the Endocrine System - Thyroid



The thyroid gland is an endocrine gland in your neck.
It makes two hormones that are secreted into the blood: thyroxine (T4) and triiodothyronine (T3).
These hormones are necessary for all cells in the body to work normally.



Thyroid disorders are very common and tend mainly to occur in women, although anybody - men, teenagers, children and babies, too - can be affected. About one in 20 people has some kind of thyroid disorder, which may be temporary or permanent.



The T4, or rather the T3 derived from it, and the T3 secreted directly by the thyroid gland influence the metabolism of your body cells. In other words, it regulates the speed with which your body cells work.
If too much of the thyroid hormones are secreted, the body cells work faster than normal, and you have hyperthyroidism.
If you become hyperthyroid because of too much secretion of the hormones from the thyroid gland, the increased activity of your body cells or body organs may lead, for example, to a quickening of your heart rate or increased activity of your intestine so that you have frequent bowel motions or even diarrhoea.



On the other hand if too little of the thyroid hormones are produced (known as hypothyroidism), the cells and organs of your body slow down.
If you become hypothyroid, your heart rate, for example, may be slower than normal and your intestines work sluggishly, so you become constipated.
What can go wrong with my thyroid?


  • Hypothyroidism (underactive thyroid) - not enough thyroxine is produced for the body’s needs.
  • Hyperthyroidism (overactive thyroid) - too much thyroxine is produced for the body’s needs.
  • Hypothyroidism is the most common disorder.What are the most common symptoms of the most common thyroid disorders that I might experience?

    Hypothyroidism: tiredness, feeling cold, weight gain, poor concentration, depression.
    Hyperthyroidism: weight loss, heat intolerance, anxiety, and, sometimes, sore and gritty eyes.
    Sometimes there are very few symptoms. A blood test from your doctor will confirm whether or not you have a thyroid disorder.

    What other disorders are there?
  • Thyroid eye disease – this affects some people who have an overactive thyroid due to Graves’ disease.
  • Nodules or swellings – these lumps can stop the thyroid gland from working properly, or are simply uncomfortable.
  • Thyroid cancer – this is very rare, but it is important to ask your doctor to check any lump in your neck.
  • Having a baby can sometimes trigger a thyroid disorder. This is known as post-partum thyroiditis. It is usually temporary but can return each time you have a baby..
  • Can thyroid disorders be treated? Yes – your thyroid disorder and many of the symptoms, too, can be treated. Most thyroid disorders are treated with daily medication. There are other treatments for those thyroid disorders that cannot be controlled with medication.


Click below for a Presentation - Thyroid