What’s the big deal?
- Hypothyroidism is linked to unusually high prolactin levels. Prolactin is a hormone that controls your breastmilk. If you have too much of it, it can actually prevent you from ovulating! What’s even trickier is that you can still get normal periods, even though you aren’t ovulating. It can also cause you to have irregular periods. These problems can definitely disrupt your fertility.
- Your body needs about 14 days to prepare your uterus for a fertilized egg. This is called the “luteal phase”. Hypothyroidism can cause a disorder in which this phase is too short – you may actually have a successfully fertilized egg, but it’s lost very early in your pregnancy because your uterus lining is too immature and can’t sustain it. You can have this extremely early “miscarriage” when you’d normally get your period, so you may not even know anything’s wrong.
- Hypothyroidism is linked to ovarian cysts. These cysts can cause problems with your fertility, since they can get in the way of your egg’s release and fertilization.
- If you get pregnant, your baby’s thyroid isn’t fully developed until about 20 weeks in. That means it’s relying on your thyroid hormone levels to grow. So if you have untreated hypothyroidism, your baby’s thyroid levels will suffer too. That’s why most physicians prefer to treat thyroid issues instead of waiting, even if you only have subclinical (very mild) hypothyroidism.
- An overactive thyroid (hyperthyroidism) can also cause irregular cycles or no ovulation at all. However, it’s more dangerous once you’re actually pregnant – it can cause miscarriages and other complications.
How it’s tested
Some symptoms of thyroid problems are fatigue, weight gain, constipation, loss of sex drive, hair loss, dry skin, loss of periods, irregular cycles and miscarriages. To diagnose, we usually do a physical exam, thyroid ultrasound, and several blood tests.
The most sensitive way to investigate is indirectly, by measuring your TSH levels. TSH (Thyroid Stimulating Hormone) is the “thermostat” for your thyroid. It tells your thyroid how hard to work. So if your thyroid is sluggish, your brain will detect that and raise your TSH levels to kickstart the thyroid. (That’s why a higher than normal TSH suggests that your thyroid isn’t going fast enough – also known as hypothyroidism.)
Traditionally, TSH levels from 0.5 to 5.0 are considered normal. If your levels are higher, we diagnose and treat you for hypothyroidism. If you don’t have any symptoms, we consider that subclinical (very mild) hypothyroidism. However, some researchers have recently suggested we should treat even subclinical hypothyroidism when your TSH is over 2.5. There’s still some controversy about this, so your doctors may not always agree.
When the TSH is elevated, your doctor will often ask for additional tests to look for the antibodies that would indicate that this is the autoimmune form of hypothyroidism.
Here’s a rundown of the hormones we test:
- TSH: This hormone is the “thermostat” for your thyroid. It tells your thyroid how hard to work. It’s measured automatically, and should be measured more than once because it can fluctuate a lot. When you’re trying to get pregnant, most clinics will automatically check this, even if you don’t have symptoms of thyroid issues.
- T4: This hormone is produced by your thyroid. It controls your body’s metabolism. If it’s low, you’ll sometimes have low metabolism symptoms and hypothyroidism. If it’s high, you may have high metabolism symptoms and hyperthyroidism.
- T3: This is a second hormone produced by your thyroid. It’s similar to T4, but it has an even stronger effect on how your body uses energy. It should be tested before treatment starts.
- TRAb: These are your thyroid receptor antibodies. This count specifically lets us diagnose (or rule out) Grave’s disease.
Note: try not to get too worried if you have mildly positive test results: because your body’s natural hormones can sometimes seem like a thyroid issue, even a “borderline” diagnosis may not actually be serious. Get follow-up tests, talk to your doctor or get a second opinion if you’re concerned.
If you have antithyroid antibodies, separating blood testing may be necessary to detect them (and figure out if there’s an underlying condition).
Wait, antithyroid antibodies what?
Antibodies are the “police” of your body: special cells that deal with bad stuff. If you have thyroid issues like hypothyroidism, these cells can be present in your body as they try to combat your thyroid problem.
There’s actually nothing wrong with having these antibodies. They won’t harm your fertility. But in some cases, they’re a warning sign that your body’s autoimmune response is too aggressive (a condition called Hashimoto’s thyroiditis), which means it could “turn against” an egg before or after implanting.
So if your doctor detects a high level of antibodies, it’s a reason to investigate further by measuring your “attack” cells: natural killer (NK) cells, and T-cells. Those are the cells that can actually cause fertility challenges. In other words, these antibodies aren’t the problem: they’re just the messenger.
Usually, we’ll discover that you have antithyroid antibodies while testing and diagnosing your hypothyroidism symptoms. However, sometimes you can have a hypothryoidism case that’s so mild it’s called “subclinical” – it barely even exists, and causes no symptoms that would alert you (or your doctor) to check for antibodies.
That’s why you should alert your doctor if you have a family history of hypothyroidism, even if you’ve never had any symptoms.
Once you’ve been diagnosed, treating thyroid issues isn’t too difficult, and the prognosis is usually good.
Hypothyroidism is treated with a synthetic form of thyroid hormone called Levothyroxine. It can take some time to get the dose right, so often you’ll have a follow-up blood test 4-6 weeks later. (That’s about how long it takes for your TSH to adjust to the Levothyroxine, or for any change in the dose.) Monitoring is important to make sure you aren’t getting too little or too much.
The good news? Levothyroxine has few impurities, very few side effects and produces almost no allergic reactions!
Once you’re pregnant, we’ll usually increase the dose to compensate for how your pregnancy hormone interacts with your TSH.
You may have also heard of “natural” thyroid hormone. Normally, your thyroid gland secretes a hormone called T4, which your body then converts into a more beefed-up hormone called T3. Natural thyroid hormone contains both T3 and T4, which could be dangerous because the levels are harder to predict. That’s why most endocrinologists prefer synthetic T4: it allows your body to decide for itself how much T4 to convert into T3.
Treating hyperthyroidism and Grave’s disease
If your condition is detected before you get pregnant, the common treatment option is radioactive iodine. Your thyroid “drinks” the iodine and shrinks. However, we can’t treat you with iodine if you’re 10 weeks pregnant or farther along, because at that point it would shrink your baby’s thyroid too!
If you’re already pregnant, the standard is to administer the medication PTU. It treats your baby’s thyroid as well, but in a positive way. It’s usually safe, effective, and has minimal side effects.
There are also oral medications for hyperthyroidism, like propylthiouracil, Celestone, and methimazole. They can often get your hyperthyroidism under control within a few months! However, some medications aren’t appropriate if you’re already pregnant, so talk to your doctor.
Finally, you can have your thyroid removed completely. That’s called a thyroidectomy. Because your thyroid will no longer exist to produce hormones, you’ll have to take replacement hormones.
Although miscarriages, premature deliveries and pre-eclampsia are higher if your hyperthyroidism isn’t under control, the outcome is usually great if you’re being treated!
Treating antithyroid antibodies
Antithyroid antibodies don’t need to be treated, since they aren’t technically a problem. However, if your NK and T-cell counts reveal an underlying autoimmune condition, it can be treated with IVIG therapy (which is sort of like getting regular, intravenous blood transfusions).