Your thyroid gland is small structure in the front of your neck, just above your collarbone. Its importance for your health and well-being is far out of proportion to its size. The thyroid makes hormones that regulate the rate at which your cells burn nutrients and perform various functions. When the thyroid is underactive in hypothyroidism, or overactive in hyperthyroidism, many bodily functions are affected. Although changes caused by thyroid problems are similar for both sexes, men can experience certain symptoms that differ from those in women.

Fertility

In both hyperthyroidism and hypothyroidism, men might experience fertility problems. When a man has an overactive thyroid, he may produce sperm with poor movement, called low motility. This could interfere with his ability to father a child, according to a study published in June 2004 in "Best Practice and Research: Clinical Endocrinology & Metabolism." **These changes in sperm are reversed in most cases when treatment brings thyroid hormones back to normal 4.

Hypothyroidism can also cause fertility problems in men, because hypothyroidism may lead to overproduction of a pituitary hormone called prolactin. Too much prolactin may cause a drop in the production of testosterone, which supports sperm production. A study published in the winter 2012 issue of the "Urology Journal" found that men with hypothyroidism had low sperm counts that could interfere with conception, compared to a control group 5. These changes are often reversible with treatment.

Sexual Function

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Changes in thyroid function can also have significant effects on sexual function in men with either hypothyroidism or hyperthyroidism, according to a study published in the December 2005 issue of "Journal of Clinical Endocrinology & Metabolism." In a group of 34 men with hyperthyroidism, 50 percent experienced premature ejaculation, while about 15 percent had erectile dysfunction that interfered with their ability to maintain an erection 5. In a group of 14 men with hypothyroidism, about 65 percent had erectile dysfunction, delayed ejaculation and low libido, or poor sex drive 5.

Although the exact mechanisms through which low or high thyroid hormone levels affect sexual function in men are not fully understood, these symptoms improved in many of the men in both groups when their thyroid problems were treated.

Other Symptoms

In addition to problems affecting reproductive function, men with thyroid problems share many symptoms women experience. When thyroid hormone is too high, a man may feel warm or sweat excessively in normal room temperatures. Weight loss may occur despite no changes in diet. Nervousness, anxiety, jitteriness and trembling of the hands are also common. The heart rate is often fast and commonly perceived as pounding or fluttering in the chest.

A man with hypothyroidism may feel especially cold, even in a warm room. Weakness, fatigue, weight gain, constipation, depression and sluggish are common.

Thyroid cancer can also develop in men or women and may cause no symptoms at first, but could lead to hoarseness or difficulty swallowing in later stages.

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Both hypothyroidism and hyperthyroidism are considerably more common in women than in men, as is thyroid cancer. Hyperthyroidism occurs in only 0.2 percent of men, compared to about 2 percent of women. Hypothyroidism is also more common in women and rare in men, occurring in 4 to 5 women in 1,000 and 0.6 to 0.9 men per 1,000. Thyroid cancer is about 3 times more common in women than men, notes the American Cancer Society 8.

If you experience problems with erectile function or ejaculation, or have any of the other symptoms of a thyroid problem, consult your doctor or a specialist in endocrinology, who can help you determine the best course of action.