Thyroid hormone plays multiple vital roles in human physiology, which include basal metabolic rate enhancement, protein synthesis in the cellular structure, maturation of neural development and controlling long bone development. Thyroid hormonal function provides a significant impact on every human cellular development. Female reproductive health also depends upon thyroid hormone secretion. It has been noticed in many cases, female infertility is a resultant of unidentified or untreated thyroid disease.
Thyroid hormonal disorder related to female fertility can occur due to anovulatory cycles, defective luteal phase, increase the level of prolactin and sex hormonal imbalance. Thyroid hormone is essential for female fertility, conception, to continue successful gestational phase, healthy and successful pregnancy.
Doctors usually prescribed to diagnose the thyroid hormone level in case of a woman is facing an irregular menstrual problem or want to conceive but the familial history of thyroid hormonal disorder, or in case of unable to conceive even after one year of unprotected intercourse, recurrent miscarriage history. Altered thyroid hormone levels are associated with disturbed folliculogenesis, a lower fertilization rate, and lower embryo quality.
Thyroid disorder is diagnosed through evaluation of T3, T4, and Thyroid stimulating hormone (TSH) level. In addition, thyroid autoimmune disease diagnosis is conducted by assessing the thyroid peroxidase (TPO) antibodies, thyroglobulin/antithyroglobulin antibodies, and thyroid stimulating immunoglobulin (TSI). The positive finding of thyroid autoimmune disease increases the miscarriage risk double than the normal level of thyroid hormone.
The association of hyperthyroidism related infertility is relatively low in comparison with hypothyroidism related infertility. It has estimated that approximately 0.9% to 5.8% infertility is associated with hyperthyroidism. However, the detailed pathophysiology is still unclear.
Infertility or recurrent miscarriage history have association of hypothyroidism. In 2 to 4 percent of the female have hypothyroidism at their reproductive age. In medical testing, hypothyroidism is classified as subclinical hypothyroidism and clinical hypothyroidism. In subclinical hypothyroidism, the diagnostic report displays an increased level of TSH with normal T3 and T4 level. Whereas, a significantly high level of T3 and T4 in association with an increased level of TSH is noticeable in clinical hypothyroidism.
The prevalence rate of subclinical hypothyroidism is more than the clinical hypothyroidism. Approximately 0.7% to 43% female fertility problem has a direct association with subclinical hypothyroidism. Anovulation or increased level of prolactin is the primary reason for subclinical hypothyroidism related infertility. Increase production of thyrotropin-releasing a hormone in females having hypothyroidism stimulates the pituitary gland and increase the secretion of TSH and prolactin. Therefore, hypothyroidism associated hyperprolactinemia is a common laboratory finding. Hyperprolactinemia impairs the Gonadotropin-releasing hormone pulsatility and consequently impairs the ovarian function. All these consequences lead to female infertility.
It is necessary to mention that the association of hypothyroidism related hyperprolactinemia is not always equivalent. Stress is one of the major cause which triggers hyperprolactinemia. Therefore, hypothyroidism affected the infertile female need to correct the TSH and prolactin hormone level along with the stress-free lifestyle to reverse infertility.
Currently, thyroxine hormone therapy is the treatment choice for hypothyroidism. This hormonal therapy normalizes the TSH level and concurrently prolactin level also minimized. Approximately 76.6% of hypothyroidism female successfully conceive within 6 weeks to one year by opting this hormone therapy.