Thyroid Hormones

This Section is for Registered patients only

Please Log in

Thyroid is your metabolic accelerator. Increase your thyroxine and the more fuel you burn, take the foot off the thyroid pedal, the less fuel you burn. However, your thyroid hormone is much more than just an accelerator pedal. It regulates how fast your brain goes, how fast your reflexes are and what your day feels like. The majority of the natural thyroid gland output is T4 ( Levothyroxine). But a good proportion of the output is also T3 (Triiodo thyronine). There are de-iodinases at the tissue level to convert T4 to T3. However some tissues depend on your thyroid gland output of T3. The activity of the deiodinase hormones depend on the tissue and on genetic factors and may well contribute to the sensitvity of individuals to different levels of thyroid hormone replacement. If the Thyroid gland has been destroyed ( Radioactive -iodine treatment/ surgery / severe thyroiditis) your body is entirely dependent on the tissue enzyme for its T3. If you were born with the wrong set of genes, however high your T4 ,your T3 may be low.

Do I need T3 prescription in addition to Levothyroxine (T4)?

The evidence regarding T3 prescription is not very clear. Very few studies have actually shown benefit. Most of the benefit has been psychological benefit. However trials are designed to study populations and may not predict the requirement for the individual. The answer to your question can only be determined after tests.

Why do I feel dreadful despite taking my tablets at the right time?

Your endocrinologist needs to spend some time with you to determine the answer to this question. Do you have any other Medical conditions? Are you absorbing your medications well? Is your Deiodinase enzyme working adequately? Are there any psychological issues? Are you sleeping well?

Did you know?

During pregnancy, the baby takes over the mother’s thyroid to ensure the baby’s brain grows properly? If you don’t have a thyroid, your baby may be at risk as your thyroid cannot increase production.


Science Direct 2015

What will your endocrinologist do?

  • Take a good history
  • Examine you and your thyoid
  • Check for T4, TSH, T3 and antibodies
  • Check other hormones if required

Immune Attack on the Thyroid

The Thyroid gland like other organs is susceptible to immune attack. This may occur

  • during a viral infection where the gland becomes the battlefield of your body’s robust war on a virus
  • in Autoimmune attack ( Hasimotos disease or Graves disease)


The gland may become swollen , tender and may produce more hormone initially as all the stored hormone is poured out into the blood stream. Under sustained attack, the gland gets damaged and stops producing thyroid hormone

Graves disease

This is a specific auto immune disease where the antibodies act like Thyroid Stimulating hormone (TSH). This leads yto enlargement of the gland and persistant increased production of T4 and T3 from the gland.


  • Patient Thyroid
Expand All | Collapse All
  • 1. I have all the symptoms of an underactive thyroid

    The symptoms of an underactive thryoid overlap with a variety of symptoms found in non thyroid abnormalities.

    However it is important to look at your symptoms in detail and thy and explain your symptoms. Is it the thyroid or could there be other causes?

    It is also important to study your thyroid over time and establish how the thyroid responds. A single blood test taken on a busy stressed day may not give us the picture. Several blood tests are required.

    Further move your doctor will need to look at other hormones. Often abnormalities in one will signal changes in other hormones.


  • 2. Do you prescribe T3 (Liothyronine)?

    Yes I do.. However this is only to a small proportion of people who do have low T3 levels or as a Trial to see if it works. T3 is an expensive medication and if your levels are low, you may be able to get it on the NHS. However if your levels are normal, you may need to purchase it and it may work out to about £40 per month.

  • 3. My thyroid keeps swelling up and then shrinks

    This is likely to be due to inflammation and blood flow. When the thyroid is angry (Inflammation), the blood flow increases and the gland swells. this is not any cause for concern. In due course, the thyroid will settle down to its normal size although in a small proportion it may still remain slightly more enlarged.

  • 4. What are the side effects of the medicaiton?

    Agranulocytosis (around 1 in 10,000)

    The most important side effect is agranulocytosis. This occurs when the white cell count in your blood falls, due to the effect of medication. This will reduce your ability to defend yourself against infection. If you have a SORE THROAT, MOUTH ULCERS OR PERSISTENT INFECTION, please approach your doctor for a blood count.

    Allergies ( Around 1 in 1000)

    Skin rash, peeling of the skin, blotchy red rash can all be due to the tablet. Rarely it can be more serious like steven- Johnson reaction

    Liver Function abnormalities

    Occasionally, your liver enzymes can be raised.

  • 5. Help.. I am pregnant...!!!

    Thyroid Hormone at the right level is crucial for the bay's development. If you are unexpectedly pregnant

    1. Contact your doctor and inform the same day. Contact your consultant and inform same day.
    2. Have a blood test done urgently for thyroid functions (in the same week)
    3. Do not stop your tablet unless told to do so.
    • If you have an underactive thyroid and you are on thyroxine, your dose of thyroxine may need to increase around 40% through pregnancy
    • If you have an overactive thyroid, your medication may need to be changed and your dose may need to be changed to ensure your hormone levels are optimal.