The thyroid is a small gland in the front of the neck. It makes hormones that regulate growth and metabolism. These hormones affect nearly every body function. Thyroid hormones can influence:

  • body temperature
  • weight
  • cardiovascular health
  • fertility

Hypothyroidism occurs when the thyroid gland does not produce enough hormones. If your thyroid hormone levels are too low, you may have fatigue, digestive problems, sensitivity to cold temperatures, and menstrual irregularities. The condition can be managed with medication. If left untreated, though, hypothyroidism can lead to many complications. These include heart problems, nerve injury, infertility and in severe cases, death.

Your thyroid hormone level can impact your cardiovascular health. You may have a slow pulse, abnormal heartbeats, and weakened pulse.

One study found that hypothyroidism can decrease the volume of blood pumped out by the heart in each beat by 30 to 50 percent. Low levels of the triiodothyronine (T3) thyroid hormone are also associated with heart failure.

Fortunately, most cardiac complications related to hypothyroidism can be treated. This involves using the proper medication to correct your thyroid function.

Serious hypothyroidism can lower the kidney’s function. This is often due to decreased blood flow to the kidneys. You may have less ability to excrete water and absorb sodium. As a result, blood levels of sodium may be unusually low.

Replacing thyroid hormones can fix these complications. But if extremely low hormone levels persist, recovery from these renal problems can take longer.

Hypothyroidism can cause problems with the nervous system, such as muscle weakness or nerve injury. These can lead to:

  • breathing difficulties
  • hoarseness
  • trouble walking
  • trouble talking
  • pain in the hands and feet

People with untreated hypothyroidism may also be more prone to carpal tunnel syndrome.

Hypothyroidism reduces fertility in both men and women. Thyroid hormones regulate the metabolism of sex hormones, which control the production of sperm and eggs. In men, low levels of thyroid hormones have been linked to erectile dysfunction, abnormal sperm shape, and decreased libido. Men with hypothyroidism often also have low levels of testosterone.

Evidence from multiple studies suggests that menstrual problems are three times more frequent in women with hypothyroidism. Variation in flow and irregular menstruation are the most common symptoms. Women with autoimmune thyroid disorder are also more likely to have infertility.

Studies suggest that not enough thyroid hormones during pregnancy may cause problems. It can increase the risk of a miscarriage or other complications, like preeclampsia or preterm birth.

If you have hypothyroidism, tell your doctor if you’re pregnant or planning to become pregnant. That way, proper treatment can begin as soon as possible. You may need to adjust the dose of thyroid medication frequently during pregnancy, so regular thyroid tests are important.

If you notice symptoms of hypothyroidism, talk to your doctor. Being proactive and treating hypothyroidism early can help avoid any major complications.