Thyroid Gland Problems and Symptoms

There are two thyroid hormones T3 (tri-iodothyronine) and T4 (thyroxine). In healthy circumstances when thyroid hormone levels in the blood drop more TSH (thyroid stimulating hormone) is secreted and this TSH, in turn, stimulates the thyroid to release more hormone.

Thyroid hormone exists in the bloodstream in either of two forms:

1. ‘free’ hormone molecules which are biologically ‘active’.
2. ‘bound’ hormone molecules which are inactive – these are hormone molecules waiting to become active.

What is usually measured when ‘standard thyroid screening blood tests’ are carried out?
Usually total T4 (thyroxine) level is checked. This result will include both active and inactive hormone levels.
Sometimes a TSH level alone may be checked.

Comments on ‘standard’ thyroid testing
My preference is to measure the active thyroid hormone levels. Hence I prefer to test both free T3 (FT3) and free T4 (FT4) along with TSH. Thyroid antibodies are also useful in indicating an evolving thyroid problem. T3 is actually much more potent than T4. Occasionally someone will have an adequate free T4 level, and normal TSH level but a low free T3 level so it really is worthwhile looking carefully at the thyroid in cases of unexplained fatigue.
If TSH alone is measured it will miss the person whose body cannot increase TSH levels in response to falling T4 or T3 levels.

What about ‘reverse T3’
Reverse T3 is similar in chemical makeup to normal T3 but it is a mirror image or isomer –think of the analogy of right versus left-hand gloves. The reverse T3 will bind to and block the ‘normal’ T3 binding site on the cell wall and prevent it from its normal activity. The clinical significance of reverse T3 is controversial – there is a suggestion that it helps to prevent weight-loss in starvation conditions such as famine. There definitely are colleagues who find measuring reverse T3 of value but I rarely check reverse T3 because there is no way directly to treat the high reverse T3. In addition  reverse T3 is a relatively expensive investigation.

Adequate iodine levels are important to the body’s manufacture of thyroid hormone. Iron and zinc are among the important substances in the conversion of T4 into the much-more-potent T3.

How is thyroid disease treated ?

The standard medical treatment for hypothyroidism is thyroid hormone replacement which involves a compound called thyroxine which is a synthesised form of T4. Many patients who have thyroid underfunctioning live long, happy and productive lives on T4 and never darken the door of a practice such as mine.

Armour Thyroid

There is a small percentage of patients who, anecdotally, fail to tolerate T4 well and some of them do much better taking Armour Thyroid which is pork derived, and is listed in the US Pharmacopoeia. Armour Thyroid is an extract of porcine glandular thyroid and contains both T4 and some T3. It is significantly more expensive than straightforward thyroxine/Eltroxin and that really doesn’t matter if it’s just one month’s treatment; but over the years costs mount up. Definitely life changing for a small number of people to shift from thryxine to Armour Thyroid but I would advise considering the move carefully.