Hello and welcome to the zero to finals podcast.

My name is Tom and in this episode I'm going to be talking to you about thyroid function tests.

And you can find written notes on this topic at zero to finals.com slash thyroid function tests

or in the endocrinology section of the zero to finals medicine book.

So let's get straight into it.

Hyperthyroidism refers to when there are raised thyroid hormones, which are tri-iodothyronine,

or T3, and thyroxine, which is T4.

Hypothyroidism refers to low levels of the thyroid hormones.

Thyroid function tests can be used to check for abnormal thyroid function and determine the cause.

Let's start with the hormonal tests.

Thyroid stimulating hormone, or TSAsh is used as a screening test for thyroid disease.

When the T-SH level is abnormal, tri-iodothyronine or T3 and thyroxine or T4 can be measured to gain more information.

Primary hyperthyroidism is where the thyroid behaves abnormally and produces excessive thyroid hormones.

The thyroid stimulating hormone level will be suppressed by the high T3 and T4, causing a low Tsh level.

Secondary hyperthyroidism is where the pituitary gland behaves abnormally and produces excessive

TSA or thyroid stimulating hormone, for example due to a pituitary adenoma.

Excessive TSAsh stimulates the thyroid gland to produce excessive thyroid hormones.

Therefore, T-3 and T-4 will all be raised.

Primary hypothyroidism is where the thyroid behaves abnormally and produces inadequate thyroid hormones

negative feedback on the pituitary is absent and this results in increased production of thyroid

stimulating hormone the perjutority is producingstimulating hormone to try and get a response

out of the thyroid, which is not producing enough thyroid hormones.

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