Maria Bührle is the senior physician at the Department for Endocrine Surgery at the surgical clinic of the Albertinen Hospital in Hamburg. Her specialist field: the treatment
of thyroid diseases.

https://www.albertinen.de/krankenhaeuser/albertinen_krankenhaus

Why is the thyroid gland referred to as ‘a small organ with a great effect’?

Maria Bührle:

Hormones vitalise us – both physically and mentally. They are responsible for that ‘burst of energy in the morning’ or for enabling us to concentrate well. It can easily be deduced what happens when the thyroid gland is hypo or hyper active – meaning, not having the right levels of thyroid hormones in our blood. This affects many levels of the body, for example the heart rate. Our heart beats faster if we have to much hormones in our blood. The thyroid gland also plays a significant role in weight gain and weight loss. To little hormones in the body can result in weight gain, too much hormones can cause patients to rapidly lose weight.