To understand how hypothyroidism influences fertility, first you need to know that the thyroid gland produces two key metabolic hormones: T4 (thyroxine) and T3 (triiodothyronine).
This butterfly-shaped gland is located at the front of the neck, just below the Adam’s apple.
Although there are many thyroid conditions, in this article we will focus on hypothyroidism and its impact on female fertility.
What is hypothyroidism and how does it affect fertility?
Hypothyroidism occurs when the thyroid does not produce enough T3 and T4. In women it can disrupt ovulation, cause irregular menstrual cycles, and complicate conception.
Do not self-medicate: before taking any medication, consult a Reproductive Medicine specialist. They will evaluate your case and increase your chances of pregnancy.
Key symptoms in women trying to conceive
- Extreme fatigue
- Unexplained weight gain
- Cold intolerance
- Dry skin and brittle hair
- Irregular or absent menstrual cycles
- Mild depression or persistent constipation
If you notice any of these changes, share them with your doctor. Recurrent miscarriages or difficulty conceiving can be warning signs.
Most common causes of hypothyroidism
- Autoimmune thyroiditis (Hashimoto’s)
- Radiation therapy to the head or neck
- Thyroid surgery
- Iodine deficiency
- Medications (lithium, amiodarone)
- Pituitary disorders affecting TSH
In many cases the cause is not identified, so early diagnosis is vital.
Diagnosis before trying to conceive
The endocrinologist will measure your neck, skin, weight, and heart rate. Then they will order a blood test to measure TSH. A value above 3.5 mU/L suggests hypothyroidism.
Free T3 and T4 may also be measured to assess severity. With this data, your doctor will design a treatment plan to protect your health and that of your future baby.
Treatment options if you plan to have a baby
The standard treatment is levothyroxine, adjusted according to your weight (approx. 1.6 μg/kg per day) and lab results.
Every body is unique: consult a Reproductive Medicine specialist to determine your dose and monitor your hormone levels.
For more information, check our article Hypothyroidism and Fertility or explore Hyperthyroidism and Fertility.
Frequently asked questions
1. Does hypothyroidism cause irreversible infertility?
With treatment and TSH control, most patients regain ovarian function and can conceive naturally or with assisted reproduction techniques.
2. How do TSH levels influence embryonic development?
TSH regulates T3 and T4, essential for ovarian follicle maturation and a receptive endometrium. Keeping TSH between 0.5–3.5 mU/L improves implantation and reduces miscarriage risk.
3. Can I improve my thyroid with diet?
Include iodine (fish, seaweed, dairy), selenium (nuts), and zinc (lean meats). Avoid excessive raw goitrogenic foods like soy and broccoli. Always consult your nutritionist or endocrinologist before changing your diet.
4. Is levothyroxine treatment safe during pregnancy?
Yes. Levothyroxine is the treatment of choice: it does not actively cross the placenta and ensures adequate hormone levels. During pregnancy, your dose may be adjusted; monitor TSH every 4–6 weeks.
Sources Consulted
- American Thyroid Association. (2017). Guidelines for diagnosis and management of hypothyroidism. Thyroid, 27(3), 315-389.
- MedlinePlus. (2022). Hypothyroidism. https://medlineplus.gov/hypothyroidism.html
- de Groot et al. (2012). Management of thyroid dysfunction during pregnancy. J Clin Endocrinol Metab, 97(8), 2543-2565.
- Stagnaro-Green et al. (2011). Clinical practice guideline: thyroid disease in pregnancy. Thyroid, 21(10), 1081-1125.
Remember that every case is unique. We are with you on this journey and encourage you to consult a fertility specialist for the personalized guidance you deserve.