Thyroid

The thyroid is a butterfly-shaped gland at the front of your neck, and its hormones T3 and T4 determine how fast almost every cell in your body works – from your heartbeat and body temperature to your basal metabolic rate. The hormone TSH from the pituitary gland sets the pace; its level in the blood is the first test when doctors check the thyroid.

With an underactive thyroid (hypothyroidism), everything runs more slowly: tiredness, feeling cold, dry skin, constipation, hair loss, low mood – and a somewhat slower metabolism. The most common cause in Germany is the autoimmune disease Hashimoto's thyroiditis, which affects women much more often than men. An overactive thyroid (hyperthyroidism) shows the opposite: a racing heart, sweating, nervousness, unintended weight loss.

Many people with weight worries hope that “the thyroid” is the explanation. Medically, that's rarely the case: an untreated underactive thyroid does slow down the basal metabolic rate, but typically only adds two to five kilos – and a large part of that is retained water. Once treatment with the hormone levothyroxine (L-thyroxine) is properly adjusted, this usually returns to normal. If you gain weight despite good levels, the cause is more likely to lie with sleep, exercise and eating habits – and that's not meant as a reproach.

To do its job, the thyroid needs iodine. The German Nutrition Society (DGE) recommends 180 to 200 micrograms a day for adults; Germany is still considered a region with mild iodine deficiency. Iodised salt instead of regular salt (and little salt overall), sea fish once or twice a week and dairy products help cover your needs. During pregnancy and breastfeeding, requirements are higher – this is managed with medical support.

In newborns, thyroid function is routinely tested in the first days of life, because a congenital underactive thyroid needs to be treated early. If anything stands out about a child's growth or development, the TSH level is a standard test at the paediatrician's.