how thyroid problems affect fertility and pregnancy and how diet can help


Women are more prone to thyroid problems than men, and problems can become apparent when trying to conceive, or during pregnancy or menopause.  Levels of thyroid hormone that are less than optimal can affect the women’s chance of conceiving, or increase her risk of miscarriage or pre-term delivery.  For more about the way thyroid balance affects fertility and miscarriage, and when to get tested seethyroid fertility and miscarriage


the importance of balancing blood sugar for thyroid health

The majority of people who are hypothyroid will have autoimmune thyroid disease.  One small hospital based study showed that about half of people with autoimmune thyroid disease tested had impaired blood sugar balance

Sugar and high glycaemic index foods destabilise blood glucose, causing swings of high and low blood sugar. This stimulates production of the stress hormones adrenaline and cortisol whenever the blood sugar dips.   

High cortisol encourages muscle breakdown in order to increase glucose supply to the brain. Reduced muscle mass means slower metabolism and weight gain.  It is especially associated with abdominal weight gain.  High cortisol levels have also been shown to impair conversion of T4 to T3 which is the active thyroid hormone used by the body.  Stabilising blood sugar stabilises production of the stress hormones adrenaline and cortisol, this is mainly achieved with a diet that balances protein and carbohydrate intake, and that focusses on low glycaemic index foods.  Completing a 7 day food diary is the best way to begin looking at this.  I can then give you feedback and suggest easy changes to help bring things back in balance.

Chromium supplements may also help with blood sugar balance, and chromium levels have been shown to be low in women with PCOS who are insulin resistant However chromium supplements have also been shown to reduce insulin sensitivity in people with normal blood sugar so caution should be taken with supplements, and it’s all about getting the balance right for each individual  If you do choose or are advised to take a chromium supplement then you should take it at a different time from your thyroxine as it has been shown to reduce thyroxine absorption

Cinnamon, which can be added to some sweet dishes, and magnesium supplements have also been shown to help blood sugar balance, but the really important thing to focus on is protein and carbohydrate balance in your diet.


gluten sensitivity and autoimmune thyroid disease

Gluten is one of the proteins found in wheat, and some people are aggravated by it causing weakness in the immune system and inflammation in the digestive tract.  While the majority of hypothyroid patients will not be gluten intolerant, studies have associated it autoimmune thyroid disease.  If you have autoimmune thyroiditis you may want to consider having a Gluten Evaluation Profile blood test which includes 5 different tests of gluten sensitivity.  Then you will have a definite answer to whether or not you should avoid gluten.


vitamin D, selenium and thyroid function

Vitamin D has been shown to be a common deficiency in a range of autoimmune disorders including autoimmune thyroid disease.  If you decide to be tested for Vitamin D status then the test should be for the circulating form of calcidiol 25(OH)D.  If you need supplementation it should be in the form of cholecalciferol (D3) and should usually continue for at least 6 months for maximum benefit.  Blood calcium levels should be monitored while you are taking D3.

Selenium is required for production of thyroid hormones, and for conversion of T4 to the active thyroid hormone T3 which the body can use. Supplementation has also been shown to reduce levels of thyroid antibodies, and to significantly reduce the risk of developing thyroid disease in pregnancy if you are antibody positive 


should I take iodine or kelp?

Iodine is frequently advised as a supplement to stimulate production of thyroid hormones. This is based on the knowledge that iodine is deficient in the soil in areas where hypothyroid disease prevails. However in the UK and USA today the commonest cause of hypothyroid is autoimmune thyroiditis which is not caused by iodine deficiency.  Excess iodine also causes thyroid problems and can stimulate the development of autoimmune thyroiditis.

The mechanisms of autoimmune thyroid disease are not yet fully understood but it appears that when the thyroid gland is undergoing autoimmune stress it requires rest rather than stimulation.  Giving thyroxine appears to be beneficial in this sense and antibody levels may drop during thyroxine treatment. This has also been shown to be true for patients who have positive thyroid antibodies and normal thyroid function

However iodine deficiency is still reported in the UK. This is thought to be due to soil depletion, and because people are reducing their salt intake for health reasons.  Low levels during pregnancy can affect the baby’s brain development and have been shown to relate to lower IQ    Dietary sources of iodine include fish, shellfish, milk, cottage cheese, eggs, turkey and beans, and so this may be a safer way of ensuring adequate intake than taking supplements.

Kelp is also recommended by some practitioners for its naturally high iodine content, but the same cautions apply as for supplemental iodine.  If you have autoimmune thyroid disease I don’t advise taking iodine or kelp, or supplements containing them.  I do advise reasonable dietary intake of iodine and appropriate treatment with thyroxine medication.


foods that affect thyroxine absorbtion

Thyroxine should ideally be taken at the same time each morning 1 hour before eating breakfast.   Some supplements and foods should not be taken within 3 hours of thyroxine as they compete with thyroxine for absorption.  These include…

  • Iron supplements & multivitamins
  • Calcium supplements & calcium fortified foods
  • Soya
  • Lemon balm (may be in herbal teas)