Thyroid Problems

Hyperthyroidism Slideshow

• Thyroid Problems Overview
• Thyroid Problems Causes
• Thyroid Problems Symptoms
• When to Seek Medical Care
• Exams and Tests
• Thyroid Problems Treatment
• Medications
• Surgery
• Next Steps
• Follow-up
• Prevention
• Outlook
• Synonyms and Keywords
• Authors and Editors
• Viewer Comments: Thyroid Disease - Describe Your Experience

Thyroid Problems Overview

The thyroid gland is located on the front part of the neck below the thyroid cartilage (Adam's apple). The gland produces thyroid hormones, which regulate body metabolism. Thyroid hormones are important in regulating body energy, the body's use of other hormones and vitamins, and the growth and maturation of body tissues.

Diseases of the thyroid gland can result in either production of too much (hyperthyroidism) or too little (hypothyroidism) hormone.

• Production of thyroid hormones: The process of hormone synthesis begins in a part of the brain called the hypothalamus. The hypothalamus releases thyrotropin-releasing hormone (TRH). The TRH travels through the venous plexus located in the pituitary stalk to the pituitary gland, also in the brain. In response, the pituitary gland then releases thyroid-stimulating hormone (TSH) into the blood. The TSH travels to the thyroid gland and stimulates the thyroid to produce the two thyroid hormones, L-thyroxine (T4) and triiodothyronine (T3). The thyroid gland also needs adequate amounts of dietary iodine to be able to produce T4 and T3.

• Regulation of thyroid hormone production: To prevent the overproduction or underproduction of thyroid hormones, the pituitary gland can sense how much hormone is in the blood and adjust the production of hormones accordingly. For example, when there is too much thyroid hormone in the blood, TRH and TSH production are both decreased. The sum effect of this is to decrease the amount of TSH released from the pituitary gland and to reduce production of thyroid hormones from the thyroid gland to restore the amount of thyroid hormone in the blood to normal. Defects in these regulatory pathways may result in hypothyroidism or hyperthyroidism.

Hypothyroidism in pregnancy

Newly diagnosed hypothyroidism in pregnancy is rare because most women with untreated hypothyroidism have ovulatory problems, which make it difficult for them to conceive.

It is a difficult new diagnosis to make based on clinical observation. Many of the symptoms of hypothyroidism (fatigue, poor attention, weight gain, numbness, and tingling of the hands or feet) are also prominent symptoms of a normal pregnancy.

Undiagnosed hypothyroidism during pregnancy increases the chance of stillbirth or growth retardation of the fetus. It also increases the chance that the mother may experience complications such as anemia, eclampsia, and placental abruption.

Probably the largest group of women who will have hypothyroidism during pregnancy are those who are currently on thyroid hormone replacement. The ideal thyroxine replacement dose (Synthroid, Levoxyl, Levothroid, Unithroid) during pregnancy may rise by 25%-50% during pregnancy. It is important to have regular checks of T4 and TSH during pregnancy to make sure you are at the correct medication dose.

Hyperthyroidism in pregnancy

Newly diagnosed hyperthyroidism occurs in about 1 in 2,000 pregnancies. Grave's disease accounts for 95% of hyperthyroidism newly diagnosed during pregnancy.

As with hypothyroidism, many symptoms of mild hyperthyroidism mimic those of normal pregnancy. However, anyone experiencing symptoms such as significant weight loss, vomiting, increased blood pressure, or persistently fast heart rate should have blood tests to evaluate whether hyperthyroidism is present.

Untreated hyperthyroidism does cause fetal and maternal complications including poor weight gain and tachycardia (an abnormally fast heart rate).

Treatment of hyperthyroidism during pregnancy is primarily medical. Propylthiouracil or methimazole (Tapazole) are the usual first-line agents to block the synthesis of thyroid hormone. They appear to be equally effective and have the same rate of side effects. The rate of side effects of each medication is not increased in pregnancy.

Iodine will cross the placenta, so its use in either a thyroid scan or in treatment with radioactive iodine is prohibited in pregnancy.

One positive note for women with hyperthyroidism is that those with Grave's disease or Hashimoto thyroiditis may have improvement in their symptoms during pregnancy.

Postpartum thyroid disease

Some women may have thyroiditis that usually occurs within 3-6 months after birth. It also may occur after miscarriage. The classic clinical picture is a woman who will first have symptoms of hyperthyroidism, followed by hypothyroidism, culminating in normal thyroid function.

Women with type I diabetes have a 25% risk of developing postpartum thyroid dysfunction.

Consult your doctor if you have symptoms of hypothyroidism or hyperthyroidism after pregnancy or miscarriage.

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Thyroid Disease - Describe Your Experience

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