Thyroid hormones run metabolism, periods and, if you are pregnant, a developing brain. If you have an underactive thyroid and you are pregnant or planning to get pregnant, the NHS underactive thyroid page says tell your GP. You will need further tests, and the levothyroxine dose will likely need to change. Untreated hypothyroidism can increase the chance of pre-eclampsia, birth defects, premature birth or miscarriage. Treatment usually helps prevent those complications. That is medicine. Selenium sits beside it; it does not replace it.
UK fertility guidance is narrower than internet TSH charts: only offer thyroid function tests to people with possible fertility problems if they have symptoms of thyroid disease. Subclinical hypothyroidism was reviewed in 2026 and left as a research recommendation, not a treat-everyone protocol. Don't demand a TSH of 2.5 from a blog.
Symptoms that belong in a GP surgery, not a supplement cart
Common symptoms of hypothyroidism: extreme tiredness, feeling cold, weight gain, constipation, brain fog, low mood, dry skin or hair loss, a hoarse voice, irregular or heavy periods. They develop slowly. They overlap with TTC stress, iron deficiency, depression and “having a job”. That overlap is why you see a GP rather than order a postal hormone kit.
Overactive thyroid is a different disease with a different NHS page, and a different set of risks in pregnancy. Don't self-sort which one you have from a single TSH screenshot.
Women's Health UK's hormone-balancing guide is useful lifestyle context (sleep, stress, cycle). It is not a thyroid protocol. Iodine is relevant to thyroid hormones; that does not mean megadose iodine because you are TTC.
What the tests actually are
A GP who suspects hypothyroidism asks about symptoms and family autoimmune history, may examine your neck, and may check TSH and thyroxine (T4) in blood. Further tests and a specialist sit behind that. Reference ranges are laboratory-specific. “Optimal fertility TSH” numbers circulating on forums are not a treatment target on the NHS page. If your endocrinologist or obstetric team sets a pregnancy range, that is their letter, not this journal.
| Situation | What UK pages say | What not to do |
|---|---|---|
| Symptoms of thyroid disease while TTC | Thyroid function tests are appropriate | Ignore symptoms because “tests are not routine” |
| No thyroid symptoms, standard fertility work-up | Do not offer thyroid tests just because you are TTC | Pay a private panel to chase a number |
| Known hypothyroidism, planning pregnancy | Tell the GP; dose likely to change; untreated disease raises pregnancy risks | Stay on the old dose and add ashwagandha |
| Subclinical hypothyroidism | Research recommendation, not a nationwide treat-all rule | Start thyroxine from a forum |
Iodine, selenium and the food-supplement line
Iodine is needed to make thyroid hormone. In the UK, deficiency severe enough to cause hypothyroidism is described as rare; autoimmune Hashimoto's is the usual cause. Selenium contributes to normal thyroid function and to the protection of cells from oxidative stress — . Don't add kelp. Don't double a 200 µg selenium and a second “thyroid complex”. If you already take a formula that prints selenium and iodine, read the panel before you buy a third bottle.
Her Revive prints selenium and iodine as part of a women’s vitality formula. Levothyroxine remains levothyroxine. If you're TTC with a normal thyroid and a 90-day window, Her Fertility is the preconception stack; the couple bundle is the couples shelf. Neither is thyroid medicine.
Ashwagandha and thyroid disease can be a “ask the person who prescribed the thyroxine” conversation. Our ashwagandha vitality piece is the Revive-line article. Don't stack adaptogens onto an unstable TSH because a podcast said cortisol.
TTC practicalities
If you are on levothyroxine and you get a positive test, call the GP or midwife the same week — don't wait for the booking appointment to mention it. If you're TTC and you have new thyroid-pattern symptoms, that is a sooner-than-12-months GP visit. Take the partner. Take the current bottle. Don't stop thyroxine to “go natural for fertility”.
Folic acid 400 µg (or prescribed 5 mg) still applies. Vitamin D still applies as 10 µg in the seasons they specify. Those two are public health. TSH tinkering is not.
FAQ
Should every couple have TSH checked before trying?
Guidance does not offer thyroid tests in fertility investigation unless there are symptoms of thyroid disease. A known thyroid history is a different sentence: tell the GP if you are planning pregnancy.
My private TSH is 3.2 and the forum wants 2.5. Do I need treatment?
That debate is not on the NHS hypothyroidism page. Take the result to a GP or endocrinologist. Don't start or stop thyroxine from a blog.
Can a fertility supplement replace levothyroxine?
No. Don’t taper a prescribed dose because a tub mentions selenium.
Thyroid disease is GP and, if needed, specialist care. Nutrition can sit beside it. If you’re TTC with a stable thyroid and want a 90-day preconception formula, that is Her Fertility and, for him, Him Fertility — after the blood form, not instead of it.
How selenium in the formulas fits
Thyroid care is levothyroxine and TSH targets with a clinician. Selenium contributes to normal thyroid function. Her Fertility includes selenium at 200 µg, as does Him Fertility. Her Revive also includes selenium at 200 µg plus iodine 150 µg. Do not stack extra selenium. Flag ashwagandha with whoever manages your TSH.
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