What are the symptoms of an underactive thyroid and when should you see a doctor?

An underactive thyroid causes complaints because the body produces too little thyroid hormone. The most recognisable ones are: fatigue, feeling cold easily, weight gain, dry skin, constipation and a changed (sometimes lower or hoarse) voice. These complaints are, however, vague and not very specific; they can also belong to dozens of other conditions. Blood tests are therefore needed to confirm the diagnosis.

Many people also notice that their thinking slows down. Difficulty with memory and concentration, low mood and a general 'brain fog' can occur, sometimes even before the diagnosis has been made. The precise reason for this is not yet well understood, but it does genuinely belong to the picture of an underactive thyroid.

What is less well known is that the thyroid has a direct influence on the heart. Pumping capacity can decrease and vascular resistance can rise. This occurs even in a mild, so-called subclinical variant, in which blood values are only slightly abnormal and complaints are still absent. In people under 65 with such a mildly elevated thyroid value, there is a greater risk of cardiovascular disease, particularly when the abnormality is more pronounced.

You should see a doctor if you recognise several of the above complaints, but certainly also in these specific situations. Are you pregnant or do you want to become pregnant? Then have your thyroid function checked; even a mild disturbance can affect the brain development of the child and the course of the pregnancy. Do you have complaints that are worsening rapidly, such as extreme confusion, a dangerously low body temperature or an unstable condition? In that case there is a rare but life-threatening decompensation that requires immediate emergency care.