SLOT: Full Definition
What is infertility?
Infertility — sometimes called trouble conceiving or subfertility — is generally defined as the inability to become pregnant after 12 months of regular, unprotected intercourse (or 6 months for women over 35). It is far more common than most women realize, affecting roughly 1 in 6 couples in the United States. Infertility is a symptom, not a diagnosis: it tells you that something in the reproductive cascade — ovulation, fertilization, implantation, or hormonal signaling — is not working as it should.
For women in their 30s and 40s, the most overlooked drivers of infertility are thyroid dysfunction, hormone imbalances, and underlying autoimmunity. These are exactly the areas a root-cause clinic is built to evaluate.
What conditions cause infertility?
Many of the most treatable causes of infertility involve the thyroid and ovarian-hormone systems:
- Hypothyroidism and Hashimotos Thyroiditis — even subclinical low thyroid can disrupt ovulation, shorten the luteal phase, and increase miscarriage risk
- Polycystic Ovary Syndrome — the leading cause of ovulatory infertility in women
- Hyperthyroidism — can also impair fertility and increase pregnancy complications
- Luteal phase defect and low [progesterone]
- Elevated prolactin, often from stress or thyroid dysfunction
- Endometriosis and tubal factors
- Egg quality decline with age and oxidative stress
- Male-factor issues (responsible for roughly 30-40% of cases)
Nutrient status (iron, vitamin D, B12, folate), gut health, and chronic inflammation also play larger roles than mainstream care typically acknowledges.
When is infertility a red flag?
Seek evaluation sooner — not at the 12-month mark — if you have irregular or absent periods, a known thyroid or autoimmune condition, a history of miscarriage, signs of PCOS, or you are over 35. Recurrent pregnancy loss (two or more miscarriages) always warrants a full workup including thyroid antibodies, full thyroid panel, hormones, and clotting factors.
What typically helps
A root-cause workup at Modern Thyroid Clinic looks beyond TSH alone — full thyroid panel, antibodies, sex hormones at the right cycle days, insulin and glucose, prolactin, and key nutrients. Optimizing thyroid function (often using Levothyroxine or combination therapy), addressing insulin resistance, restoring ovulation, and correcting deficiencies can dramatically improve fertility outcomes. Medications such as Clomiphene may be appropriate for some patients. Many women who were told they were "normal" go on to conceive once their thyroid and hormones are properly optimized.
Common symptoms
Common questions
Can a thyroid problem really cause infertility?
Yes — and it is one of the most overlooked causes. Even mild hypothyroidism or elevated thyroid antibodies can interfere with ovulation, implantation, and early pregnancy. Most fertility specialists target a TSH below 2.5 in women trying to conceive, yet many women are told their TSH of 3.5 or 4 is "normal." At Modern Thyroid Clinic, we run a full thyroid panel including antibodies and optimize thyroid function before and during pregnancy, which often improves both conception rates and pregnancy outcomes.
How long should I try before getting tested?
Standard guidelines recommend evaluation after 12 months of trying if you are under 35, and after 6 months if you are 35 or older. However, you should not wait if you have irregular cycles, a known thyroid or autoimmune condition, signs of PCOS, a history of miscarriage, or any reason to suspect a hormonal imbalance. Earlier testing is not an overreaction — it gives you more time and more options. A baseline thyroid and hormone panel is reasonable from the moment you start trying.
What labs should I ask for?
A thorough fertility workup goes well beyond a basic TSH. We typically order Free T4, Free T3, reverse T3, TPO and thyroglobulin antibodies, FSH, LH, estradiol, progesterone (timed to the luteal phase), prolactin, AMH, fasting insulin and glucose, vitamin D, B12, ferritin, and a full metabolic panel. Pelvic ultrasound and a partner semen analysis round out the picture. The goal is a complete view, not a single number.
Think you might be dealing with this?
Talk to a Modern Thyroid Clinic specialist about your symptoms, labs, and next steps.
Book a Discovery CallThis content is for educational purposes only and is not medical advice. Consult a licensed clinician for diagnosis and treatment. Content on this page does not create a doctor-patient relationship with Modern Thyroid Clinic.