How Thyroid Impacts Women’s Fertility

The inability to conceive is often a distressing experience for couples. Approximately 15% of couples have difficulty conceiving. Of these couples, a male factor is present in almost 60% (a contributory cause in 40% and a sole factor in 20%).

Male fertility is dependent upon an intact hypothalamic-pituitary-testicular axis to initiate and maintain quantitatively and qualitatively normal spermatogenesis, maintain normal secondary sex gland function, and sexual function.  Thus, it is surprising how infrequently infertile men have a recognizable endocrinopathy.

Also read: What you need to know about thyroid surgery 

HPO axis:

Fertility in women is tightly regulated by the hypothalamic-pituitary-ovarian (HPO) axis.  Any derangement of the HPO axis results in menstrual irregularities and ovulation disorders, with consequent sub-or infertility.  In addition, endocrine dysfunction of the thyroid, pancreas, adrenal, and pituitary gland frequently disrupts the HPO axis and adversely influences overall fecundity.

An abnormal endocrine milieu is not conducive to a healthy pregnancy.  Between 10% and 23% of repetitive pregnancy, losses are attributed to endocrine dysfunction. Menstrual irregularity and ovulatory dysfunction, with resultant impairment infertility, may, therefore, serve as a protective mechanism against maternal and fetal complications.

Thyroid gland failure and varying degrees of dysfunction are quite common among the female population. Because initial signs and symptoms are vague, ambiguous, and often seen in various underlying disorders, thyroid disease is often missed in is early stages.

Sadly enough, patients may be seen on multiple occasions in their physician’s office with similar complaints and maybe even treated for the secondary consequences such as infertility, hypercholesterolemia, anaemia or depression.  It is very necessary to raise the index of suspicion in the highest risk population to enable a timely diagnosis and treatment.

How does thyroid affect fertility?

In women

  • may cause anovulation & menstrual irregularities
  • may cause luteal phase defect (LPD)
  • may cause hyperprolactinemia

In men

  • may cause low sperm count
  • may reduce sperm motility (movement)

Thyroid disorders in females:

Thyroid dysfunction is more common in women than in men. Thyroid antibodies are present in approximately 5% of women.  Clinical manifestations of thyroid disease can be subtle and insidious.  Various reproductive disorders ranging from abnormal sexual development to menstrual irregularities and infertility have been associated with thyroid disorders.

  • Subclinical hypothyroidism often manifests as menstrual irregularities, particularly menorrhagia and luteal phase defects, and can cause female subfertility or infertility.
  • Overt hypothyroidism is associated with amenorrhea and anovulatory infertility.

Routine screening for occult thyroid dysfunction in an infertile population revealed that 5.1% had abnormal thyroid function tests.  In another series, 2.3% of women who failed to conceive over a year had elevated thyroid-stimulating hormone (TSH) levels and ovulatory dysfunction.

Hyper-and hypothyroidism can result in menstrual irregularities, compromise fertility, and, if unrecognized in pregnancy, can be associated with increased fetal morbidity and mortality.  Goitre is more common in women because of an increased renal loss of iodine results in a mild iodine deficient state, which sensitizes the thyroid gland to the growth-promoting properties of TSH.

 The degree of iodine deficiency is usually insufficient to induce frank hypothyroidism, but it may induce goitre formation during puberty and pregnancy when there is increased iodine demand.  Renal loss of iodide in pregnancy increases threefold.  Goitres caused by iodine deficiency is prevalent in women who reside in certain geographic areas, particularly high-altitude regions, and in those who consume a diet rich in goitrogens.

The consumption of iodized salt is an easy, convenient preventive measure, but iodized salt may not be easily available.  With improve diagnostic tests, early diagnosis, and treatment fertility can be restored with normalization of the thyroid axis.

Image result for hypothyroidism

The frequency and type of menstrual irregularities associated with thyroid disorders largely depend on the extent of the disease and timing of diagnosis during the course of the disease.  With the availability of ovulation-inducing agents, there is a possibility that thyroid disorders may be overlooked in women presenting with menstrual irregularities and anovulation.

Pregnancy in women with overt thyroid disease is uncommon, but when it does occur, it can be fraught with complications and have grave consequences. Therefore, evaluation of the thyroid axis in women presenting with fertility problems is imperative.

Endocrine dysfunction can impair fertility and alter pregnancy outcome. Undiagnosed and untreated thyroid disease can be a cause for infertility. Once the diagnosis is secured, most endocrine disorders are reversible or can be adequately managed to restore fertility and decrease associated pregnancy complications.

It is clinically evident that women suffering from thyroid disorders are associated with a frequent occurrence of menstrual disturbances and impaired fertility, and these abnormalities are improved by restoring the euthyroid state.

Autoimmune thyroid disease (AITD) cause cellular damage and alters thyroid gland function by humoral and cell-mediated mechanisms.  It has been suggested recently that autoimmune abnormalities are closely related to a reproductive failure.

Content Courtesy: Abbott India Ltd

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