Hypothyroidism is a disorder in which there is a lack of normal thyroid production or secretion of thyroid hormone. In other words, the thyroid gland is underactive so there follows an underproduction of thyroid hormone. Your thyroid is a small bowtie or butterfly-shaped gland, located in your neck, wrapped around the windpipe, and is located below the Adam's Apple area. The thyroid produces several hormones, of which two are key: triiodothyronine (T3) and thyroxine (T4). The thyroid hormone is responsible for controlling the activity as well as energy use of the body's organs -- in fact, almost every metabolic process is affected by it.

It is unlikely one person will have all the following symptoms, but most will have several:

Who Has it?

Both sexes of adults are affected, but it is more common in women. The disorder occurs in nearly 2% of women and only 0.2% of men and although it can occur at any age -- and even though incidence increases with age (past age 60) -- it is screened for in newborns. (An unborn child may be affected if the mother is producing an inadequate secretion of thyroid hormone.)

You are at risk for thyroid problems if you have a family member with a thyroid problem, have another pituitary or endocrine disease, if you or a family member have another autoimmune disease, if you've been diagnosed with Chronic Fatigue Syndrome or Fibromyalgia, you're female, over 60, just had a baby, near menopause or menopausal, a smoker, have been exposed to radiation or other chemicals such as flouride or perchlorate, been treated with lithium, or eat too much soy foods.

Additionally, hypothyroidism can result from hyperthyroidism. Hyperthyroidism is a condition that occurs when the amount of thyroid hormone in the blood is too high, which leads to an overall increase in a person's metabolism that can cause a number of problems. There are a number of causes for this disorder. While there are cases of unknown causes, most cases are caused by one or more of the following:

How Does it Impact Fertility?

Many women with thyroid disease worry about whether they can even become pregnant. It is true that thyroid problems can sometimes be an impediment to getting pregnant. Women may receive a diagnosis of hypothyroidism for the first time during a fertility evaluation. According to Dr. Rubenfeld, a thyroidologist and Founding Chairman of the Thyroid Society for Education and Research, fairly common problems caused by thyroid dysfunction are anovulation (no ovulation, or release of an egg) and menstrual irregularities. With no egg to fertilize, conception becomes impossible.

In addition, because of hypothyroidism, some women experience a short luteal phase. The luteal phase is the timeframe between ovulation and onset of menstruation. The luteal phase needs to be of sufficient duration (a normal luteal phase is approximately 13 to 15 days) to nurture a fertilized egg, and too-short a phase can cause what appears to be infertility, but is in fact failure to sustain a fertilized egg, with loss of the very early pregnancy at around the same time as menstruation would typically begin.

Dr. Rubenfeld said that "the mechanisms by which thyroid problems interfere with fertility are often unknown, but there is no question that other aspects of thyroid function affect fertility." For example, hypothyroidism can cause an increase in prolactin, the hormone produced by the pituitary gland that induces and maintains the production of breast milk in a post-partum woman. Excess prolactin has a negative effect on fertility. In addition, while there have been few systematic studies of this, there is clear evidence that hyperthyroidism can affect male fertility by causing a low sperm count or reduced sperm motility in men. This condition is, however, treatable.

Miscarriage Rates

Some women are concerned that a husband or partner's thyroid problems will interfere with the ability to sustain a pregnancy. Again, according to Dr. Rubenfeld, evidence exists that some men with hyperthyroid may have a lower sperm count or sperm motility than normal. However, if the woman becomes pregnant, there is no concern that her partner's thyroid disease will affect her pregnancy. If, a woman does not seek treatment for a thyroid condition, it is possible that she will have a higher chance of miscarriage.

How is it Treated?

The goal of treatment for both men and women is to provide the body with enough thyroid substance for efficient body function. Medical evaluation may be necessary for several months to establish the correct dose of thyroid replacement. Your doctor will prescribe thyroid-replacement hormones, generally levothyroxine. Dosage requirements will depend on age, weight, sex, capacity of thyroid function, other drugs you take and intestinal function. Research suggests that men and women who actively treat their hypothyroidism with thyroid-replacement hormones can, in most cases, restore fertility.

Treatment in Pregnancy

Changes in estrogen levels have effects on thyroid function. This is one key reason that thyroid hormone dosage requirements can change during pregnancy, a period of tremendous hormonal fluctuation. Because it takes approximately six weeks for the thyroid dosage requirements to fluctuate in response to the change in estrogen from pregnancy, so the first prenatal visit should take place no earlier than six weeks, and no later than 12 weeks. From that point on, thyroid levels should be checked at least every three months. If dosages are changed, additional follow-up blood tests should typically occur within five to six weeks after the dosage change.

Above all, regular visits with the doctor to monitor thyroid hormone levels are important. Careful and regular monitoring is essential for women who have no thyroids due to surgical removal. Women who have hypothyroidism before becoming pregnant may need to increase their dose of levothyroxine by up to 50%. In very rare cases, women may develop hypothyroidism during pregnancy and need to be treated with levothyroxine in full replacement doses to reduce the risk of stillbirth. The developing baby is not affected when the pregnant woman takes thyroid hormones. The pregnant woman with hypothyroidism should be monitored regularly and doses adjusted as necessary.

Taking thyroid hormone is the process of replacing something that a woman's body -- especially when pregnant -- would normally already have. The greatest danger is the hypothyroid woman who thinks taking all drugs during pregnant -- including thyroid hormone -- is bad for her baby, and discontinues her thyroid hormone replacement. During pregnancy, it is even more important to make sure to take the proper dosage of thyroid replacement, as this ensures that the mother's thyroid function will meet the demands of pregnancy.

Testing during Pregnancy

Because untreated hypothyroidism is a serious problem for the unborn child, all pregnant women should be tested for thyroid function. Elevated levels of estrogen during pregnancy cause thyroid hormone levels to rise. Therefore, a pregnant women with an underactive thyroid may have what appears to be normal levels of thyroid hormones, but she may actually be hypothyroid. A blood test showing elevated TSH levels, however, is a reliable indicator of an underactive thyroid, even in pregnancy.

Journal Articles:

Management of hypothyroidism during pregnancy. Clin Obstet Gynecol 1997 Mar;40(1):65-80

The male and female reproductive systems in hypothyroidism. In: Braverman LE, Utiger RD eds. Werner and Ingbar's The Thyroid: A Fundamental and Clinical Text. 6th ed. Philadelphia, PA: JB Lippincott Co. 1991; 1052-1063

Maternal Hypothyroidism and Fetal Developmen, Utiger, RD. In: New England Journal of Medicine 1999 Aug:19, Vol 341. No 8.

For More Information:

American Thyroid Association

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