Thyroid and Fertility: A Tiny Gland that Might Unlock Some of the Mysteries of Our Fertility Woes
A Fertile Heart Approach to Understanding How Thyroid Function Affects Estrogen and Progesterone Balance, Ovulation, Uterine lining, Prolactin Levels and the Viability of a Full-Term Pregnancy.
The thyroid is a butterfly-shaped gland nestled in your neck that directs a cascade of hormones meant to support steady energy levels, smooth metabolism and affecting everything from how fast your heart beats to how well your ovaries function.
Why We Need to Request a Full Thyroid Panel When Aiming for Baby Making:
When I ask my clients if their thyroid function was tested, alarmingly many women tell me that their work-up at the fertility clinic didn’t include thyroid testing. What I also often hear is that women who were tested have been simply told that their TSH numbers are fine. Within normal range. But they seem to be experiencing all the symptoms of impaired thyroid function such as poor circulation, fatigue, recurrent miscarriages and more.
Which is why it’s crucial to remember: when we’re having trouble conceiving, testing TSH levels does not reveal all we need to know.
This page hopes to clarify the level of testing that’s needed, foods and supplements that support an optimal level of thyroid function.
We’ll start with the stuff you’re probably most eager to learn such as testing, thyroid friendly foods and supplements.
Then I strongly suggest that you also take some time to read through a bit deeper explanation of how this humble gland works. The more you know the more inspired you’ll be to take action and take good care nourishing this hardworking part of your baby making system.
Testing: A full thyroid panel will insure that we are not missing more subtle imbalances that could make a difference in conception and a full term pregnancy.
Here’s what to ask for:
- TSH (Thyroid-Stimulating Hormone) is useful since it can indicate an underactive thyroid (high TSH) while low TSH might mean your thyroid is working too hard.
- Free T3 and Free T4: These are the active hormones. Free T3 is the “doer,” while Free T4 is the “warehouse stock” ready to be converted.
- Thyroid Antibodies (Anti-TPO – Anti-Thyroid Peroxidase Antibodies and Anti-Tg Anti- Thyroglobulin Antibodies): If your immune system is attacking your thyroid, it could be quietly sabotaging your fertility efforts.
- Reverse T3: This hormone slows down your thyroid, it’s a kind of brake. High levels can mean your body isn’t utilizing thyroid hormones efficiently enough.
Here is an overview of the cascade of hormones involved in thyroid function:
The Hypothalamus: The Brain’s Control Center
The process starts in the hypothalamus, the part of the brain that detects when the body needs more thyroid hormones. When it senses a need, it releases TRH (Thyrotropin-Releasing Hormone) into the bloodstream. TRH travels to its next destination: the pituitary gland.
The Pituitary Gland: The Master Messenger (Some of us are familiar with the pituitary since it’s involved in FSH release)
The pituitary gland located just below the brain, receives the TRH signal and responds by releasing TSH (Thyroid-Stimulating Hormone) into the bloodstream. TSH is like a messenger delivering the instructions for the thyroid gland, to produce hormones.
The Thyroid Gland: The Hormone Factory
The thyroid gland, shaped like a butterfly at the base of your neck, receives TSH and gets to work. It uses iodine (from your diet) and other nutrients to produce two main hormones:
- T4 (Thyroxine): The storage form. Think warehouse
- T3 (Triiodothyronine): The active form that directly affects how your body uses energy .
Although T4 is produced in greater amounts, it must be converted into T3 in various tissues to become active. This conversion ensures your body gets the precise amount of energy it needs.
Thyroid and Fertility: How Thyroid Hormones Influence the Hypothalamic-Pituitary-Ovarian (HPO) Axis and Every Part of Your Menstrual Cycle
The HPO axis is the hormonal control center for the menstrual cycle, and as noted earlier, the thyroid plays a key role in that system, affecting estrogen and progesterone balance, ovulation, uterine lining and implantation, prolactin levels and the viability of a full term pregnancy.
Let’s break it down:
Impact on Estrogen and Progesterone Balance
Thyroid hormones directly influence the production and metabolism of estrogen and progesterone, the two key hormones regulating your menstrual cycle:
- Hypothyroidism (Low Thyroid Function):
- Elevated Estrogen: Reduced thyroid hormone levels slow the clearance of estrogen from the body, leading to excess estrogen relative to progesterone. This imbalance can cause irregular, heavy, or prolonged periods (menorrhagia).
- Low Progesterone: Impaired ovulation due to hypothyroidism can result in lower progesterone levels, further disrupting the luteal phase (the second half of the cycle).
- Hyperthyroidism (Overactive Thyroid):
- Low Estrogen: Excess thyroid hormones speed up estrogen metabolism, leading to lower estrogen levels. This can cause lighter or missed periods (oligomenorrhea or amenorrhea).
- Reduced Progesterone: Ovulatory issues can also reduce progesterone levels in hyperthyroidism.
Thyroid Hormones and Ovulation
The thyroid is essential for ovulation, the release of an egg from the ovary:
- Hypothyroidism: The lack of sufficient thyroid hormones can cause the ovaries to stop releasing eggs regularly (anovulation), leading to irregular cycles or difficulty in conceiving.
- Hyperthyroidism: Excess thyroid hormones can similarly disrupt ovulation due to hormonal imbalances in the HPO axis.
Uterine Lining and Menstrual Flow
Thyroid hormones influence the uterine lining (endometrium), which sheds during menstruation:
- Hypothyroidism: Excess estrogen thickens the uterine lining, potentially leading to heavy and prolonged periods (menorrhagia) or spotting.
- Hyperthyroidism: Reduced estrogen levels may lead to a thinner uterine lining, resulting in lighter or absent periods.
Prolactin Levels
Thyroid function also affects prolactin, a hormone produced by the pituitary gland that influences ovulation and menstrual cycles:
- In hypothyroidism, high TSH levels can stimulate prolactin production, leading to:
- Suppressed GnRH, which reduces FSH and LH, causing irregular or absent periods.
- Milk production (galactorrhea) in non-pregnant or non-breastfeeding women.
Thyroid Antibodies and Autoimmune Impact
If autoimmune thyroid disease (e.g., Hashimoto’s or Graves’) is present, the immune system’s attack on the thyroid can disrupt the menstrual cycle via systemic inflammation, which:
- Impairs ovarian function.
- Alters hormone signaling.
- Affects uterine receptivity and embryo implantation.
Common Menstrual Issues with Thyroid Dysfunction
- Hypothyroidism:
- Heavy, prolonged periods (menorrhagia).
- Irregular cycles (oligomenorrhea).
- Difficulty conceiving due to anovulation.
- Premenstrual syndrome (PMS) exacerbation.
- Hyperthyroidism:
- Light or absent periods (amenorrhea).
- Short cycles (polymenorrhea).
- Fertility challenges due to ovulatory dysfunction.
Now that we know the power of this small valiant gland, let’s look at the thyroid-tending we can do, to insure it gets all it needs before taking on the labor intensive job of pregnancy. Here is a list of thyroid friendly and not-so friendly foods.
