I am trying to conceive. How low should my TSH be?

Hello,

Welcome to icliniq.com.

I read your query and can understand your concern.

Your laboratory reports show a TSH (thyroid-stimulating hormone) level of 6.8 µIU/mL (high) and a free T4 (thyroxine) level of 0.8 ng/dL (low-normal). This indicates under-treated hypothyroidism, meaning your current Levothyroxine dose (75 mcg) is insufficient.

The goal TSH levels vary depending on the stage:

1. For the general population, the target is between 0.5 and 4.0 µIU/mL.

2. For women planning pregnancy or trying to conceive, it should be ≤2.5 µIU/mL.

3. During the first trimester of pregnancy, the target is even tighter at 0.1 to 2.5 µIU/mL.

So, yes, before trying to conceive, your TSH should ideally be ≤2.5, because even mild hypothyroidism (subclinical or overt) increases risks of:

1. Difficulty conceiving (due to anovulation or luteal defects).

2. Miscarriage.

3. Preterm birth.

4. Neurodevelopmental issues in the baby.

Your doctor’s plan to increase levothyroxine is absolutely correct.

Persistent symptoms like fatigue, constipation, and weight gain are classic hypothyroid (a condition where the thyroid gland produces too little thyroid hormone, slowing down body metabolism) symptoms that persist until T4 and TSH normalize. But there can be additional reasons for continued fatigue despite treatment:

1. Poor Levothyroxine absorption (see below).

2. Low iron or ferritin.

3. Vitamin D or B12 deficiency.

4. Adrenal fatigue or low cortisol.

5. Depression or sleep disturbance.

6. Other hormonal imbalances, such as PCOS (polycystic ovarian disease), hyperprolactinemia (excess prolactin hormone causing menstrual and fertility problems).

So, yes, checking vitamin D, ferritin, B12, and morning cortisol is sensible if symptoms persist after thyroid correction.

Levothyroxine absorption issues are common. To get consistent levels:

1. Take it on an empty stomach, at least 30 to 60 minutes before breakfast or three to four hours after dinner.

2. Avoid calcium, iron, multivitamins, soy, or coffee within four hours of dosing.

3. Stick to one brand; switching between brands can cause fluctuations because of small differences in bioavailability.

4. If absorption remains poor, liquid or soft-gel formulations are better absorbed, especially if you have GI (gastrointestinal) issues or take acid-suppressing medication.

Hypothyroidism can mimic or exacerbate PCOS features:

1. It can cause irregular or heavy periods, anovulation, and weight gain.

2. It can increase prolactin, which suppresses ovulation.

3. It worsens insulin resistance, indirectly leading to cystic-appearing ovaries.

So, some women diagnosed with PCOS actually have thyroid-related cycle irregularity that resolves when thyroid levels normalize. Once your TSH is well-controlled, cycles often become regular again and ovulation returns, improving fertility naturally.

Iodine and Selenium trace elements are essential but must be balanced carefully. Iodine is essential for thyroid hormone synthesis, and adequate intake through iodized salt or prenatal vitamins is usually sufficient. Extra iodine supplements should be avoided unless a deficiency is confirmed, as excess iodine can worsen autoimmune thyroiditis.

Selenium helps convert T4 to T3 (triiodothyronine) and reduces thyroid inflammation; 100 to 200 µg per day from dietary sources such as Brazil nuts, fish, or eggs is generally sufficient. Supplementation should only be considered if dietary intake is poor or a deficiency is confirmed. In cases of Hashimoto’s thyroiditis, selenium may modestly lower antibody levels, but this should be discussed with your endocrinologist before starting supplements.

Vitamin D deficiency is very common in hypothyroidism and can worsen fatigue, low mood, and immunity. It is best to maintain a vitamin D level above 30 ng/mL (75 nmol/L). Morning cortisol testing can help rule out adrenal insufficiency, especially if you have persistent fatigue, dizziness, or low blood pressure. Correcting these deficiencies can improve your energy and overall hormonal stability.

Before trying to conceive, follow this preconception and pregnancy planning checklist:

1. TSH ≤ 2.5 µIU/mL.

2. Free T4 Upper-normal range.

3. Prenatal vitamins with folic acid, iodine (~150 µg), and selenium if advised.

4. Monitor TSH every four to six weeks after dose change, then every six to eight weeks during pregnancy.

5. The Levothyroxine dose is expected to increase by ~25 to 30 % once pregnant (early pregnancy raises T4 demand).

6. Avoid switching brands mid-pregnancy. Keep the dose brand constant for stability.

7. Tablet Folic acid 5 mg, 1 tablet at night for the preconception period till the end of the first trimester.

8. Inomel-F sachet (health supplement), one sachet at night for three months.

I hope I have answered your question.

Let me know if I can assist you further.

Regards.