Why the target range is tighter
In everyday life a TSH of up to about 4 mU/l counts as normal. When you are trying to conceive we draw the line considerably tighter and aim for a value below 2.5 mU/l.
The reason lies in the first weeks of pregnancy: the baby only begins producing its own thyroid hormones from the twelfth week. Until then it depends entirely on the mother – during the very phase in which the nervous system is being laid down. A supply that is sufficient for you may be too little for two.
At a glance
- Target range: TSH below 2.5 mU/l – tighter than in everyday life
- Also relevant: TPO antibodies, which increase the risk of miscarriage
- Subclinical cases are treated too: when trying to conceive, usually yes
- Before IVF or ICSI: have your thyroid adjusted beforehand
- Under one roof: gynaecology and fertility care
- Appointment: book online or call us on +43 1 5333 654
What we check before a pregnancy
We measure TSH and fT4 as well as TPO antibodies. An ultrasound scan additionally shows whether the thyroid is structurally abnormal.
If the TSH is above the target value, we start with a low dose of levothyroxine and re-check after four to six weeks. As a rule the value is then where it should be – without you noticing anything.
The role of TPO antibodies
Around one in ten women has TPO antibodies without ever having had symptoms. For fertility they are still relevant: women with detectable antibodies have a higher risk of early miscarriage and of developing hypothyroidism in the course of pregnancy – even if the TSH is currently normal.
We therefore do not treat the antibodies themselves, but we monitor more closely and intervene earlier if the TSH begins to rise.
Not only the woman
In men, too, a pronounced thyroid dysfunction can impair sperm quality. It is far less often the decisive factor, but where conception has been unsuccessful for a longer time it belongs in the work-up – and is just as easy to test.
Frequently asked questions
My TSH is 3.2 – is that bad?
Not for everyday life, but if you are trying to conceive the value is above the target range. A low-dose tablet is usually enough to bring it below 2.5. We then re-check after four to six weeks.
Do I have to keep taking levothyroxine after the birth?
That depends on your initial results. If treatment was started only because of the pregnancy and there are no antibodies, it can often be stopped again afterwards. With Hashimoto’s it usually continues. We check a few weeks after the birth and decide together.
Should I take iodine if I want to become pregnant?
Iodine requirements rise considerably in pregnancy. Most pregnancy vitamins therefore contain iodine, which makes sense at this dose. If you have known Hashimoto’s thyroiditis, we discuss this individually.