What does the thyroid do?
The thyroid is a butterfly-shaped gland in the neck that produces thyroid hormones: primarily T4 (thyroxine) and the active form T3. These hormones control metabolism, the rate at which cells burn energy. A well-functioning thyroid keeps that process in balance. An underactive or overactive thyroid disrupts it.
The thyroid is controlled by TSH (thyroid-stimulating hormone), released from the brain (pituitary gland). TSH is therefore the most sensitive measure of thyroid function: if the thyroid produces too little hormone, TSH rises to make the gland work harder. A high TSH indicates an underactive thyroid (hypothyroidism); a low TSH indicates an overactive one (hyperthyroidism).
Thyroid symptoms: why so difficult to recognise?
An underactive thyroid produces complaints that come on slowly and insidiously: fatigue, feeling cold, a slow heart rate, weight gain, dry skin, constipation, muscle aches, and difficulty concentrating. Because the symptoms worsen gradually and overlap strongly with other conditions, including stress, sleep deprivation, and depression, hypothyroidism is regularly identified late.
What to measure in a thyroid test?
The foundation is TSH. If TSH is abnormal, Free T4 (FT4) is involved: this gives insight into how much thyroid hormone is actually circulating in the blood. For a more complete picture, particularly with suspected autoimmune conditions such as Hashimoto's, thyroid antibodies (TPO antibodies) are also relevant.
At Bloodworks, the Thyroid, Energy & Metabolism package offers TSH, Free T4, Free T3, and Reverse T3, a complete picture of thyroid function, including the conversion from the inactive T4 to the active T3 form.
Want to have your thyroid tested?
The Thyroid, Energy & Metabolism package gives a complete picture of your thyroid function.
Measuring fatigue: looking beyond the thyroid
Persistent fatigue rarely has a single cause. Alongside the thyroid, ferritin (iron stores), vitamin D, vitamin B12, and cortisol are all markers that may be relevant in the context of fatigue complaints. Those who want to investigate fatigue seriously would do well to combine multiple markers. The Bloodworks Fatigue & Sleep package is designed for this, eight markers in a single blood draw.