Your thyroid gland is in the neck, and secretes hormones that regulate growth and metabolism Metabolism is the thing that controls how quickly you burn fat When the thyroid is underactive, it doesn't produce enough hormones.

This affects a lot of things in your body. it can make you need more sleep than normal, feel the cold more easily, cause depression and weight gain, and cause bad memory among many other problems.

There is medication that can help, if you are treated by your doctor.

An underactive thyroid is also known as Hypothyroidism and causes low levels of the thyroid hormone (thyroxine) in the blood. The thyroid gland is located in your neck and when it is underactive it produces low levels of this hormone.

When there is insufficient thyroxine produced in the body, metabolism slows down. This leads to weight gain, muscle aches, tiredness, depression, slow mental and physical reactions, constipation, being sensitive to the cold, dry skin, brittle hair and nails and irregular periods (NB: That list is not exhaustive)

Hypothyroidism can occur in anyone, but it is more common in women than men (around 15 in 1000 women and 1 in 1000 men will develop the condition). There is also a condition known as congenital hypothyroidism, it occurs in about 1 in every 4500 babies. In most western countries this is routinely tested for at birth using the heel prick test.

Hypothyroidism is usually caused by an autoimmune reaction, where your body attacks the thyroid gland causing inflammation. It can also be caused by treatment for thyroid cancer.

Hypothyroidism is usually balanced out using thyroxines prescribed by your doctor. It may take a few variations in doses to find the right thyroxine level, but once this has been achieved your symptoms should level themselves out.