The thyroid gland is a structure found in the mid-neck region in both men and women. Its hormones regulate body metabolism and energy use. Two primary categories of problems can occur with thyroid function.
In hypothyroidism, the thyroid is underactive. Men with hypothyroidism often experience symptoms of a lowered metabolic rate, including decreased energy and weight gain. There is quite a bit of overlap in potential symptoms of low testosterone and hypothyroidism. Hypothyroidism is typically treated with thyroid replacement, such as levothyroxine (Synthroid). Thyroid-stimulating hormone (TSH) levels are typically high (over 3.0 µIU/mL) in men with hypothyroidism.
In hyperthyroidism, the thyroid is overactive. Symptoms often include weight loss, sweating, and heart palpitations. In hyperthyroidism, the reason for the elevated thyroid hormone levels needs to be investigated. Possible sources include Hashimoto’s thyroiditis and tumors of the thyroid gland. Thyroid ablation therapy is typically used to treat hyperthyroidism. TSH levels are typically low (less than 0.4 µIU/mL) in men with hyperthyroidism.
Both hyperthyroidism and hypothyroidism can be detrimental to normal sperm production, but thyroid problems are a rare cause of male infertility. I recommend that thyroid studies be done in male fertility patients only if there are suspicious symptoms present: recent significant weight gain or loss, abnormally low or high energy levels, and sweating or palpitations.
Normalization of abnormal thyroid function can improve semen parameters and fertility in men with significant thyroid dysfunction. Mild thyroid abnormalities do not generally result in fertility abnormalities.
The initial screening test for men with symptoms suggesting thyroid abnormalities is the TSH (thyroid-stimulating hormone) test. TSH is the hormone from the anterior pituitary that stimulates the thyroid gland to produce thyroxine (T4), which is then converted into triiodothyronine (T3). The normal range for TSH is 0.4–3.0 µIU/mL.
If the TSH level is abnormal, you should undergo a full evaluation by an endocrinologist or your primary care physician to make sure that there are no tumors or other medical issues involved. At that time, T3 and T4 levels should be drawn. Normal T3 (triiodothyronine) is 80–230 ng/dL. Normal T4 (thyroxine) is 5–14 mcg/dL.
Some male fertility specialists choose to treat thyroid problems themselves, but I usually have an endocrinologist or primary care physician treat these issues. These patients will typically require lifelong management and monitoring.