Findings of a new study have shown that a slightly underactive thyroid may influence a woman's ability to get pregnant and offer a potential treatment for those with infertility problems.

The Thyroid Gland

The butterfly-shaped thyroid gland, which lies at the base of the neck, releases thyroid hormones that control the metabolism of the body and regulate vital functions of the body such as breathing, cholesterol amounts, muscle strength, heart rate, and temperature levels.

The thyroid-stimulating hormone (TSH) stimulates the thyroid gland to produce more hormones when needed.

Underactive Thyroid Gland

Higher levels of TSH indicate an underactive thyroid gland. Individuals with underactive thyroid gland produce an insufficient amount of hormones that are needed for optimal functioning of the body. Symptoms of the condition include weight gain, tiredness, a feeling of depression, sensitivity to cold, dry skin or hair, and muscle aches.

TSH And Unexplained Infertility

Now, a new study suggests another potential effect of an underactive thyroid gland. Researchers found that women with unexplained infertility tend to have higher levels of the TSH compared with women who did not conceive because of known issues.

Unexplained infertility happens when couples are unable to get pregnant after months of trying and medical evaluation does not show the reason for their infertility. About 12 percent of women in the United States who are between 15 and 44 years old have difficulty becoming or staying pregnant. Of the couples who are unable to conceive, between 10 and 30 percent have unexplained infertility.

"About 6% of married women aged 15 to 44 years in the United States are unable to get pregnant after one year of trying (infertility). Also, about 12% of women aged 15 to 44 years in the United States have difficulty getting pregnant or carrying a pregnancy to term, regardless of marital status (impaired fecundity)," the U.S Centers for Disease Control and Prevention said.

Researchers of the study found that nearly twice as many women having difficulty getting pregnant due to the unexplained cause had TSH level greater than 2.5 mlU/L compared with their counterparts whose inability to get pregnant was attributed to male factor infertility.

Researchers said that further study is needed to find out whether or not treating women with higher TSH levels with thyroid hormone may improve their odds of getting pregnant.

"Women with UI have higher TSH levels compared to a control population," study researcher Pouneh Fazeli, from the Harvard Medical School in Boston, and colleagues wrote. "Further studies are warranted to determine if treatment of high-normal TSH levels decreases time to conception in couples with UI."

The findings were published in the Endocrine Society's Journal of Clinical Endocrinology & Metabolism.