Christine Sullivan, Natural Fertility Support Specialist, Brisbane - Ph 3857 8515

The Impact of Thyroid Health on Your Fertility

BY IN Uncategorized On April 23, 2016

Thyroid Health in Fertility

Thyroid Health Essential for Your Fertility

Thyroid Health is Essential for Your Fertility

If you have been unsuccessfully trying to have a baby for some time, before you embark on invasive medical procedures and spend thousands of dollars for Assisted Reproductive Technology, along with the standard preconception checks, ensure that your thyroid is functioning at its best.

Many couples don’t realize that good thyroid function is necessary for both male and female fertility, the ability to conceive and to maintain a pregnancy.  Unfortunately, many GPs and fertility specialists rarely include comprehensive thyroid testing as part of a preconception assessment.

An under (or over) functioning thyroid can prevent you from achieving that much desired pregnancy.  While there are many and varied reasons for infertility, sub-optimal thyroid function may be that “missing link” especially for those with no specific reproductive problems and have been diagnosed as having “unexplained infertility”.

The prevalence of thyroid dysfunction is relatively high in the general population and is often undiagnosed.  I find that a very high proportion of the patients I see with fertility issues have sub-optimal thyroid function and there is increasing evidence of the significant effects of thyroid function on fertility in men and women.  The good news is that most of the sub-clinical thyroid problems are reversible.

A full thyroid evaluation is essential, and should be done as soon as possible for anyone wanting to conceive, especially if –

  • There is any family history of thyroid problems
  • There have been any previous miscarriages
  • The woman has an irregular menstrual cycle
  • It has taken more than six months to conceive.

What Does the Thyroid Gland Do?

The thyroid gland is located near the front of the throat, just below the voice box & just above the collar bones. Every cell in the body depends upon thyroid hormones for regulation of the body’s metabolism, blood calcium levels, energy production, fat metabolism, oxygen utilization, balance of other hormones & weight maintenance.

Hormones involved with thyroid function include Thyroid Releasing Hormone (TRH) released from the hypothalamus in the brain, which stimulates the pituitary gland at the base of the brain to release Thyroid Stimulating Hormone (TSH) which in turn stimulates the thyroid gland to produce the major precursor thyroid hormone Thyroxine (T4).   The majority of T4 then needs to be converted to the active hormone Triiodothyronine (T3) that enters cells to do the thyroid’s work.  This conversion happens mostly in tissues outside of the thyroid gland itself, a lot of it in the liver.   Thyroid hormones are synthesized from iodine and the amino acid Tyrosine (from protein), and the conversion from the inactive (T4) to the active (T3) form is very much dependent on the trace minerals selenium and zinc.

What Factors Impact Thyroid Health?

  • Exposure to environmental toxins – electromagnetic radiation, chemicals, pesticides, heavy metals such as mercury as well as halide minerals such as chlorine, bromine, fluorine (e.g. in water supply, toothpaste & some processed foods).  The halide minerals bind to iodine receptors preventing or reducing its use for the production of thyroid hormones.
  • Genetic susceptibility
  • High levels of stress
  • Nutrient deficiencies
  • Autoimmune disorders
  • Infections
  • Other hormone imbalances e.g. oestrogen dominance, high prolactin levels

How Does Poor Thyroid Health Affect Couples Wishing to Conceive?

Poor thyroid function or thyroid dysfunction upsets your body’s natural balance of reproductive hormones.

For Women

The menstrual cycle is much more complex than you might imagine.  It is a carefully orchestrated process that provides a small window of opportunity for an egg to be fertilised by sperm each month.

Thyroid problems can interrupt this complex process and can result in an irregular menstrual cycle or even the absence of menstruation altogether (amenorrhoea).

Anovulatory cycles

This means that you are not ovulating i.e. not releasing an egg.  Luteinizing Hormone (LH) has the task of stimulating the ovary to release the egg.  If thyroid hormone levels are not ideal they cannot support LH to do this.  If no egg is released this makes pregnancy impossible. It is still possible to menstruate regularly but not ovulate so you may not be aware of this.

Luteal Phase Problems

It takes 13-15 days to nurture a fertilized egg. If the second half of your menstrual cycle (luteal phase) is too short due to poor LH response and subsequent insufficient progesterone production (T3 is required for progesterone release from the luteal cells), a fertilized egg can’t implant securely and will end up leaving your body at the same time that menstruation would occur. This very early miscarriage is often mistaken as a regular period.

Low Body Temperature

Low thyroid function will also result in a lower basal body temperature.  The rapidly dividing cells in a little embryo require a specific temperature range for that division to take place.  If your basal body temperature is too low, the embryo may be unable to continue to grow.  This increases the risk of early miscarriage.

High Prolactin Levels

Elevated levels of Thyroid Releasing Hormone (TRH) and low levels of Thyroxine (T4) can also result in an excess of prolactin (normally produced by the pituitary gland to promote lactation) and TSH both of which will have a negative effect on fertility and can prevent ovulation or result in irregular or absent periods.

Other Hormonal Imbalances  

Reduced sex hormone binding globulin (SHBG), oestrogen dominance, progesterone deficiency, all interfere with proper reproductive hormone balance.  Oestrogen is a known antagonist to thyroid hormones so oestrogen dominance can suppress thyroid function.  Balanced oestrogen and progesterone levels will facilitate normal thyroid function and vice versa.

Loss of libido

Sex drive is influenced by a number of physical and emotional factors.  Hormones can have a powerful effect on sexual desire.  When other hormone imbalances are combined with the fatigue and mood changes associated with a thyroid disorder, it really can dampen libido.

For Men

It is just as important for men to prepare for a healthy pregnancy as it is for women.  There are many lifestyle factors that mess with the quality of the sperm which in turn affects the couple’s chances of conceiving.

Thyroid activity directly affects spermatogenesis (sperm production).  There are large numbers of thyroid hormone receptors on the steroli cells, the nurturing cells for sperm in the testes.  T3 (the active thyroid hormone) binds to these receptors so directly influences sperm production and motility.

Poor thyroid health in men can also result in reduced testosterone production, a lower libido, erectile dysfunction, poor testicular function, as well as reduced sperm numbers and motility. Both hyper and hypothyroidism produce increased levels of oxidative stress which damages the DNA integrity and form or morphology of the sperm.

In some cases hormone dysfunction, if left unchecked, can result in increased oestrogen and prolactin production in men leading to mammary enlargement and feminization.

So you can see the significant regulatory role thyroid function has in sperm production and male fertility.

Pregnancy risks

Undiagnosed and untreated thyroid problems can endanger your pregnancy and worsen pregnancy problems such as fatigue, hair loss, depression, morning sickness, preterm labour, inter uterine growth retardation, and increased risk of miscarriage.

Risks for your baby

Poor thyroid function may also put your baby at risk of a preterm birth and low birth weight.  There is also the risk of thyroid problems, impaired growth and development of the testes in male babies and possible problems with fertility as an adult.  Where severe iodine (a major component of thyroid hormone) deficiency is part of the picture, there is increased risk of cognitive problems and brain development in the baby.



  1. Do you have any of the common signs & symptoms associated with low thyroid function?
  • Inability to conceive / infertility
  • Miscarriage
  • Menstrual irregularities
  • Period pain
  • Low libido
  • Lethargy & fatigue
  • Susceptibility to the cold / cold hands & feet
  • Inability to lose weight
  • Changes in texture of skin, nails, hair, hair loss
  • Recurrent infections
  • Constipation
  1.  Is your basal temperature consistently below  36.5°C?                                                            

Often, routine blood tests may appear “normal” because the problem is occurring in the cells and not in the blood.  To make an assessment of your thyroid function, record your oral temperature at rest first thing in the morning before moving out of bed for 7 -10 days.  For women this is best done within the first 14 days of your cycle.  If your thyroid function is optimal, your temperature will be between 36° and 37° C but ideally above 36.5°C.

  1. Blood Tests

For full thyroid assessment you require readings for TSH, T4, T3, rT3 & Thyroid Antibodies (thyroperoxidase antibodies/TPO Ab and thyroglobulin antibodies/TgAb).  TRH may also be required.  For optimum fertility, ideally, your Thyroid Stimulating Hormone (TSH) level should be between 1 and 2 mIU/L, Thyroxine (T4) between 16-20 pmol/L, Triiodiothyronine (T3) between 4.5 – 6.0 pmol/L, reverse T3 around x 100 of your T3 and 0 IU/ml for thyroid antibodies.  Your doctor or naturopath can order these tests for you.

  1. Urinary Iodine                                                                                                                             

Iodine is a key component of thyroid hormone.  Excessive iodine as well as a deficiency of iodine can result in low thyroid function.  Urinary iodine should ideally be between 150-200ug/L.  Your doctor or naturopath can also order this test for you.

  1. Diet & Lifestyle

Our modern western diet is a major contributor to increasing thyroid health problems.  Foods detrimental to thyroid health include refined grains, simple sugars, soy products, peanuts & peanut products, caffeine, hydrogenated oils, cigarette smoking and alcohol.  Excessive consumption of vegetables such as cabbage, broccoli, turnips, Brussels sprouts in their raw form may block the absorption of iodine.

Exposure to heavy metals e.g. mercury (amalgam fillings) and fluoride, chlorine (water supply, toothpaste), bromine (processed foods & drinks) as well as bisphenols in plastics may also be detrimental.

Stress management is imperative.  Stress results in elevated levels of cortisol, the main hormone released by the adrenal glands.  Increased cortisol will inhibit the conversion of T4 to the active T3 hormone and will stop the active T3 entering cells sufficiently.

Exercise is beneficial as it will stimulate thyroid hormone secretion and increases tissue sensitivity to thyroid hormones.

Treating thyroid function is not a magic cure for all fertility issues but I have found that for many women (and men), once thyroid health has been improved, their fertility issues were resolved and they have gone on to have a healthy pregnancy and enjoyed the treasures of parenthood.

If you suspect that less than ideal thyroid health may be contributing to your fertility difficulties or just impinging on your health generally, take action now!



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