In many ways, the thyroid is like the man behind the curtain. You have never seen him and are not really sure what he does, but you know he’s there. You’ve heard about him, blamed him for your weight gain and for sleeping through your alarm clock, and considered that errors in his way are keeping you from getting pregnant. But how he is masterminding all of this remains unclear.

While the intricacies of the thyroid are more delicate than a lace shirt, the basics come down to a simple Goldilocks type of situation: the thyroid is working too fast, too slow, or just right. When it’s really off, you usually feel really off. Simply stated, when your thyroid is running on empty or very close to it (think flashing red light telling you to pull over ASAP), you will feel like a car without gas, putt putt puttering through your day, being tired, cold, and constipated, with dry skin and hair loss, to name a few.

On the flip side when your tank has been topped off just a bit too much, you feel like you had one too many shots of espresso. You experience insomnia, diarrhea, palpitations, hot flashes/sweating, anxiety…

However, sometimes the deviations are subtle, and your thyroid is just slightly off (medically termed subclinical). But you may not know it unless a doctor checks. While the subclinical part will usually not cause you any noticeable symptoms, it can increase your risk of miscarriage and infertility and lead to negative pregnancy outcomes. Bottom line: if your thyroid is off, it’s not only your bottom line that will suffer but also your plus one.

As a result, fertility MDs are somewhat fixated on hitting the thyroid hormone level sweet spot! We check it on nearly all of our patients pre-pregnancy and then again during pregnancy. We are somewhat OCD in getting it to the perfect point and will labor over when to start some additional medication, when to increase or decrease it, and when to stop it.

What and where is this elusive “gas producer”? The thyroid is a small butterfly-shaped gland that sits at the base of the neck. In most women who are free from thyroid disease, the thyroid is small and cannot be felt. The thyroid produces thyroid hormones (T4 and T3); these hormones travel through the blood throughout the body to target organs. Almost all of your vital organs are target organs in desperate need of a little thyroid juice! The ovaries and the uterus are also quite “thirsty.”

Thyroid hormone plays a role in regular ovulation, pregnancy implantation, and miscarriage. Additionally, babies don’t start to produce their own thyroid hormone until about 13 weeks of age (in utero). Therefore, for the first trimester of pregnancy, babies rely exclusively on their mothers. If you are borderline low making thyroid hormone, they will be super low. And given that thyroid hormone is essential for brain development, this is not an area you want to be lacking in! It is for this reason that doctors will frequently start a thyroid supplement early before the situation hits rock bottom.

While your thyroid may not be to blame for all of your problems, it’s under (termed hypothyroidism) or over production (hyperthyroidisim) may be the cause of some serious ailments. And like most autoimmune conditions (where the body basically attacks itself), women are about six times more likely to be diagnosed with thyroid disease; most of those diagnoses will be made in the reproductive years (30s and 40s).

Not only is the thyroid important for pregnancy and fertility, but the start of it’s decline often occurs during the reproductive years.  So while your tank may be running on empty because you’re burning the candle at both ends, it is always a good idea to have your thyroid level checked, particularly when contemplating pregnancy. Who knows? You may just need a little refueling to help put an end to those annoying symptoms!