The Thyroid: A Small Organ with a Big Impact
The thyroid is a butterfly-shaped gland with essential regulatory functions for the entire body. It acts as a hormone reservoir and produces triiodothyronine (T3) and thyroxine (T4), which influence metabolism, heart rate, blood pressure, and even fertility. It also produces calcitonin, a hormone that regulates calcium and phosphate levels in the blood. The release of T3 and T4 is controlled by thyroid-stimulating hormone (TSH).
The importance of the thyroid becomes particularly noticeable when it becomes imbalanced, as thyroid dysfunction can negatively affect various bodily functions, including metabolism, circulation, and reproductive health.
Thyroid Disorders and Infertility
Women experiencing infertility often undergo a long journey of medical examinations to identify the cause. While infertility has many possible causes, thyroid dysfunction can be a significant factor and should be assessed by an endocrinologist. Below, we explore the two main thyroid disorders: hyperthyroidism and hypothyroidism.
Hyperthyroidism (Overactive Thyroid)
In hyperthyroidism, the thyroid produces too many hormones, leading to an overactive metabolism. Symptoms include:
✔️ Nervousness, restlessness
✔️ Sweating, weight loss
✔️ Irregular menstrual cycles
✔️ Infertility
Hypothyroidism (Underactive Thyroid)
In hypothyroidism, the thyroid does not produce enough hormones, causing:
✔️ Fatigue, sluggishness
✔️ Increased need for sleep
✔️ Memory issues, weight gain
✔️ Dry, pale, cool skin; brittle nails and hair
✔️ Slow heart rate, weakened reflexes
✔️ Menstrual irregularities, infertility
Hypothyroidism is one of the most common causes of unexplained infertility.
How Do Thyroid Disorders Affect the Menstrual Cycle?
Thyroid disorders disrupt reproductive function and are particularly significant for women trying to conceive. Both hyperthyroidism and hypothyroidism can cause menstrual irregularities and fertility issues.
Since thyroid hormones interact closely with sex hormones like estrogen, an imbalance affects egg maturation and ovulation, reducing the chances of pregnancy. In cases of hyperthyroidism, even if conception occurs, miscarriage risk in the early months is increased.
Who Is at Risk?
Around 10% of infertile women have a thyroid disorder, most commonly hypothyroidism. Even mild or latent hypothyroidism can negatively impact fertility.
Women with thyroid antibodies or Hashimoto’s thyroiditis are significantly more likely to struggle with conception compared to those without thyroid disorders.
Diagnosing Thyroid Issues in Fertility Treatment
Thyroid testing should be a standard part of fertility evaluations, especially if:
✔️ A woman has a family history of thyroid disorders
✔️ Pregnancy has not occurred after 6 months of trying
A blood test measuring T3, T4, and TSH levels can provide crucial insights.
📌 TSH levels should ideally be in the lower normal range for optimal fertility (Zieren 2020).
It’s important to note that TSH levels can naturally fluctuate by 20–30% throughout the day. Therefore, thyroid function tests represent a momentary snapshot and should be evaluated carefully. If abnormalities are detected, further hormone and ultrasound tests are conducted.
Additionally, thyroid antibodies can be tested to screen for Hashimoto’s thyroiditis, an autoimmune condition that is the leading cause of hypothyroidism.
Treatment Options
For Hypothyroidism:
✔️ Hormone replacement therapy (L-thyroxine tablets) compensates for the hormone deficiency.
✔️ With proper treatment, many women with hypothyroidism can conceive.
✔️ Dosages require regular monitoring and adjustments.
For Hyperthyroidism:
✔️ Thyroid-suppressing medications (thyreostatics) help regulate hormone production.
✔️ Successful treatment often restores normal thyroid function, reducing its impact on fertility.
💡 For men, low libido and erectile dysfunction can also result from hypothyroidism. In some cases, correcting the hormone imbalance improves male fertility.
Why Is Iodine Essential?
Simply put: Without iodine, the thyroid cannot produce hormones.
Iodine is an essential trace element and a key ingredient for T3 and T4 production, which regulate metabolism and organ growth. Without sufficient iodine, the thyroid enlarges (goiter) to compensate for the deficiency.
Germany remains one of the most iodine-deficient regions in Europe. While iodine intake has improved over the years, at least one-third (possibly up to half) of the German population still does not get enough iodine. This long-term deficiency often goes unnoticed until more severe symptoms develop.
Ensuring Adequate Iodine Intake
Since the body cannot produce or store large amounts of iodine, it must be regularly consumed through food. The thyroid absorbs up to 80% of daily iodine intake.
✔️ Recommended daily intake: 150–200 µg (DGE)
A healthy lifestyle and balanced diet support thyroid function, while smoking, stress, and irregular routines can have negative effects.
Iodine-Rich Foods
To ensure sufficient iodine intake, focus on:
✔️ Sea fish & seafood (at least twice a week)
✔️ Dairy products (milk, yogurt, cheese)
✔️ Green vegetables
✔️ Iodized table salt
💡 Vegetarians and vegans can supplement their diets with iodine-rich seaweed.
Iodine and Pregnancy
Iodine is essential during pregnancy and breastfeeding, as both the mother and baby need adequate iodine. Pregnant women require additional iodine, which often cannot be met through diet alone. Therefore, iodine supplementation is recommended until the end of breastfeeding (Gärtner 2020).
References
Zieren HU. (2020): The thyroid as a possible cause of infertility. Interview with Prof. Dr. Hans Udo Zieren. deutsches-schilddruesenzentrum.de
German Nutrition Society (DGE): Recommended iodine intake. dge.de
German Thyroid Center: deutsches-schilddruesenzentrum.de
Gärtner R. (2020): Iodine deficiency in Germany – Affects mainly children and young women. Gyne 04/2020.
