7 key times when a woman may need her thyroid tested...
- if you're struggling to conceive
- if you are diagnosed with PCOS
- pregnancy - especially if there is a family history of thyroid problems
- after childbirth - if you feel unwell or develop anxiety or depression
- after miscarriage
- menopause - as thyroid hormones sometimes drop at this time together with reproductive hormones
- after severe emotional stress or shock
thyroid stimulating hormone (TSH) in fertility and pregnancy
Your GP will routinely measure thyroid stimulating hormone (TSH) but may not do other thyroid blood tests. TSH is regarded as the most sensitive test of thyroid health though it doesn't give a complete picture.
- TSH normal reference range is around 0.4 - 4.5 ( this varies slightly with different laboratory assays)
- for optimal fertility we prefer the TSH to be below 2
- during pregnancy we prefer below 2.5
Higher miscarriage rates have been observed when TSH is above 2.5 in the first trimester. A 2010 study of 4123 thyroid antibody negative women in southern Italy found a 2.5% higher rate of pregnancy loss when TSH was 2.5 or above. The study recommends that 2.5 should be the upper limit in the first trimester. http://www.ncbi.nlm.nih.gov/pubmed/20534758 In 2011 the same authors published a study of 3593 antibody positive women with TSH below 2.5 which showed an increased rate of preterm delivery.
It may also be wise to have additional tests of T4 and T3 done in the first trimester. This is because TSH levels are less reliable in early pregnancy - they are lower because they are suppressed by the rising levels of the pregnancy hormone hCG. From about 16 weeks of pregnancy TSH levels become a more reliable indicator again http://bmb.oxfordjournals.org/content/97/1/137.full
thyroid antibodies and miscarriage risk
If you experience miscarriage then it may also be worth getting tested for autoimmune thyroid antibodies, 2 types are usually tested
- thyroid peroxidase antibodies
- thyroglobulin antibodies
Thyroid treatment during pregnancy may reduce your miscarriage risk if you are antibody positive even if your thyroid hormone levels are normal http://www.ncbi.nlm.nih.gov/pubmed/23147711 and http://www.ncbi.nlm.nih.gov/pubmed/16621910 In 2011 a study of 3593 thyroid peroxidase antibody positive women with normal TSH showed an increased rate of preterm delivery http://www.ncbi.nlm.nih.gov/pubmed/21411559 The same year the BMJ published a review of 31 studies which reported a strong association between thyroid antibodies and miscarriage or preterm birth and suggests that treatment with thyroxine will reduce the risk. A 2012 review of 11 studies found a higher level of preterm delivery in women who were thyroid peroxidase antibody positive.
A 2013 Belgian review showed an increased live birth rate for women undoing IVF who had subclinical thyroid problems or positive antibodies when they were treated with thyroxine http://www.ncbi.nlm.nih.gov/pubmed/23327883
If you are being tested for the first time then the ideal is to have a Full Thyroid Function Profile blood test, this includes
- thyroxine (T4)
- free thyroxine,
- free triiodothyronine (T3)
- thyroid antibodies
This can be organised for you at The Doctors Laboratory in London, or at The Clinic MK. If you are diagnosed with a thyroid problem then diet can help bring you back to balance, together with the right thyroid medication. Many things affect thyroid health including sleep, overwork and stress. For more about how diet can help see diet for thyroid and fertility