Link between hypothyroidism and hyperthyroidism with infertility

Link between hypothyroidism and hyperthyroidism with infertility
Thyroid disorders can negatively impact fertility by affecting both the ability to become pregnant and the ability to carry a baby to term. In this article, we’ll break down what hypothyroidism (too little thyroid) and hyperthyroidism (too much thyroid) is and how this can impact your chances of conceiving. You can read through our general introduction about thyroid levels and fertility here.
Written by Orchid Team 
Medically reviewed by‍ Dr. Lusy Aghajanova, MD, PhD and Cristina Vidal, RN
  • Dr. Lusy Aghajanova, MD, PhD, is a reproductive endocrinologist, clinical assistant professor, and Director of the Third Party Reproduction and Endometrial Health Program at Stanford Medicine Fertility and Reproductive Health.
  • Cristina Vidal, RN, is the IVF-Donor-Surrogate nurse coordinator at Stanford Reproductive Endocrinology and Infertility with over 20 years of experience in the fertility and reproductive clinic

Hypothyroidism and fertility

Hypothyroidism is when the thyroid gland produces less thyroid hormone than normal.

The body’s metabolism slows down when the gland produces less hormone, causing different symptoms such as:
  • Irregular periods
  • Fatigue, lethargy
  • Weight gain
  • Constipation
  • Dry skin
  • Hair Loss
  • Forgetfulness
  • Feeling cold
Hypothyroidism can impact fertility by:
  • Preventing ovulation
  • Disrupting the menstrual cycle
  • Increased risk of miscarriage
  • Increased risk of premature birth
Causes of hypothyroidism

The causes could be an autoimmune disorder (Hashimoto’s thyroiditis), not getting enough iodine in the diet, after thyroid surgery or radioactive iodine therapy used to treat hyperthyroidism, or due to unknown causes.

Diagnosing hypothyroidism

Blood levels are measured reflecting elevated thyroid stimulating hormone level (TSH). Elevated TSH means the thyroid hormone is not making enough thyroid hormone, hence increased stimulation signals. The current recommendation for preconception is to achieve a TSH level <2.5. The doctor will often also check T3 Total and Free T4 levels, which may be low in hypothyroid patients, and thyroid antibodies levels, since sometimes the body can make antibodies against your thyroid.

Treating hypothyroidism

It’s important to have hypothyroidism under control if you are planning to get pregnant. Oral medication is the treatment of choice, the most common oral medication used is Levothyroxine or Synthroid daily with blood levels checked 4-6 weeks after to make sure the levels of thyroxine are adequate and that you are taking the right dose.

After getting pregnant, levels are checked again to adjust the dose accordingly. Your doctor will check levels every trimester as the thyroid hormone requirements increase in pregnancy. Close monitoring of your TSH levels will help the development of the baby during pregnancy and reduce the chances of miscarriage.

Hyperthyroidism and Fertility

Hyperthyroidism is when the thyroid gland is hyperactive, which means the thyroid gland produces more thyroid hormone than normal. The autoimmune condition, Graves’ disease, is the most common cause of hyperthyroidism.

Some of the symptoms caused by a hyperactive thyroid hormone include:
  • Anxiety
  • Nervousness
  • Mood changes
  • Sensitivity to heat
  • Weight loss
  • Palpitations
  • Sweating
  • Muscle weakness
  • Tiredness, difficulty sleeping
  • Hand Tremor
Hyperthyroidism can impact fertility by:
  • Disrupting the menstrual cycle
  • Causing the development of ovarian cysts
  • Increased risk of early miscarriage
  • Increased risk for premature birth
  • Increase risk of pre-eclampsia like symptoms
  • In men, hyperthyroidism can cause a reduction in sperm count, resulting in reduced fertility. Sperm count usually returns to normal once treated.
Diagnosing hyperthyroidism

Blood levels are measured reflecting low thyroid stimulating hormone level (TSH). Low TSH means the thyroid hormone is making too much of thyroid hormone. The current recommendation is to achieve a lower TSH level at >0.5. Your doctor will also often check the T3 Total and Free T4 levels, which may be high in hyperthyroid patients.

Treating hyperthyroidism

During pregnancy, thyroid hormone levels are frequently checked. If antithyroid drugs are needed, patients are typically kept on the lowest effective dose of their medication during pregnancy because these medications can cross the placenta.

Propylthiouracil (PTU) is the medication that can be used during pregnancy if necessary. Surgery is reserved for situations when medical management is not effective during pregnancy or if there is a suspected malignancy.

Key Takeaway

If you have concerns about your thyroid levels, or have a family history of thyroid disorder, and want to get pregnant, it is worth getting your hormone levels checked, so that any necessary treatment can be initiated. Balancing your thyroid hormone levels through medications and lifestyle interventions will greatly increase your fertility and your chances of conception.

If you are planning on starting or growing your family, check out our expert guides on all things genetics and fertility. Today, advanced genetic screening is now available to couples who want their child to have the best shot of a healthy life. Explore how Orchid helps you conceive with confidence.
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