Hypothyroidism occurs when the thyroid gland becomes underactive and does not produce enough thyroid hormones to meet the needs of the body. Hypothyroidism that is either undiagnosed or under-treated can contribute to infertility or result in miscarriage.
Hypothyroidism is common among women of child-bearing age. Studies show that women with hypothyroidism have a significantly decreased chance of achieving a pregnancy following IVF compared to patients with normal thyroid function.
The research also suggests that treating women with hypothyroidism with levothyroxine, a manufactured form of the thyroid hormone thyroxine improves pregnancy rates and reduces the risk of miscarriage. The most common cause of hypothyroidism in the U.S is Hashimoto’s thyroiditis, an autoimmune disease that causes the body to develop antibodies that attack and destroy the thyroid.
What is the Thyroid?
The thyroid, a tiny, butterfly-shaped gland located at the base of the neck, just below the Adam’s apple, has a tremendous impact on overall health. It affects the functioning of every organ in the body, guides most bodily functions, and regulates metabolic processes, body temperature, and even heart rate. When the thyroid breaks down, it can wreak havoc on the body.
Hypothyroidism occurs when the thyroid under-produces hormones. Common symptoms include:
- Fatigue and low energy
- Muscle weakness
- Weight gain
- Intolerance to cold
- Dry skin
How Does Hypothyroidism Affect Fertility?
Thyroid hormones affect both female and male reproductive health. Thyroid imbalances can cause:
- Increased rates of pregnancy loss
- Ovulatory disorders
- Irregular periods
- Preterm birth
- Lower IQs
The pituitary gland in the brain creates thyroid-stimulating hormone (TSH) that triggers the thyroid to produce two other hormones, T3 and T4. When T3 and T4 production is not at proper levels, thyroid issues can result.
Thyroid hormones are essential in all phases of egg growth, sperm maturation, and survival of a fertilized egg. T3 hormone helps thicken uterine lining (endometrium), which is a prerequisite for implantation of a fertilized egg. Moreover, T3 helps the fertilized egg move down the fallopian tubes toward the uterus for implantation.
An underactive thyroid disrupts the metabolism of estrogen, leading to increased levels of testosterone, follicle-stimulating hormone, and luteinizing hormone. Consequently, ovulation patterns change and may result in irregular menstrual cycles.
The Impact on Male Fertility
Male infertility has numerous causes—from hormonal imbalances to anatomical problems to genetic defects. Although thyroid disease is often considered a women’s issue, about one-third of hypothyroidism cases arise in men. If left untreated, hypothyroidism in men can lead to a variety of fertility issues, including:
- Decreased sperm volume and mobility
- Sperm defects
- Lower libido
- Difficulty sustaining an erection
- A reduction in male fertility hormones such as testosterone, luteinizing hormone (LH) and follicle-stimulating hormone (FSH)
Once hypothyroidism is diagnosed in a man with fertility problems, adjusting thyroid hormone levels back to normal usually restores erectile function. In most cases, issues related to sperm quantity and quality also improve over time.
How Is Hypothyroidism Treated?
Though uncurable, hypothyroidism is manageable in the majority of cases. Treatment focuses on replacing the amount of hormone that the thyroid can no longer produce to bring T4 and TSH levels back to normal.
T4 replacement can restore the body’s thyroid hormone levels and normal bodily function. Synthetic thyroxine pills contain hormones precisely like the T4 hormone the thyroid produces. Hypothyroid patients, except those with severe myxedema (life-threatening hypothyroidism), are treated on an outpatient basis. For the few patients who do not feel completely normal taking a synthetic preparation of T4 alone, the addition of T3 (Cytomel®) may be of benefit.
Collaborating with one’s health care practitioner can improve the chances of conceiving and may include measures such as:
- Checking thyroid function and testing for Hashimoto’s before trying to get pregnant
- Getting on the appropriate medication dose and keeping TSH levels below 2.5mIU/L
- Maintaining vitamin D levels in a healthy zone: 37.5–50.0 μg (1500–2000 iu)
- Getting enough selenium: 200 mcg per day
Apart from diagnosis and medication, healthy lifestyle choices promote proper thyroid function. Reducing stress is essential, as high cortisol (a stress hormone) levels inhibit thyroid hormone production.
Increasing exercise is also helpful, as it promotes the production of thyroid hormones and increases the sensitivity of the tissues to these hormones. Furthermore, modern diets play a large part in thyroid dysfunction, in particular, diets with high amounts of refined grains and sugars, soy products, peanuts, and caffeine.
Doctors typically recommend eating a healthy diet with fresh fruits and vegetables while avoiding smoking and alcohol consumption.
For more information on how hypothyroidism affects IVF, please feel free to contact us.