Struma Ovarii
What is Struma Ovarii?
Struma ovarii is a rare type of ovarian teratoma that contains functional thyroid tissue. This tissue can produce thyroid hormones even though it is located in the ovary, not the thyroid gland. The condition accounts for about 3% of all ovarian teratomas.
When the thyroid tissue in struma ovarii becomes active, it can release triiodothyronine, known as T3, into your bloodstream. This creates a situation where thyroid hormones come from your ovary rather than your thyroid. Most cases are benign, but about 5% can become cancerous. Women with struma ovarii may experience symptoms of too much thyroid hormone, a state called hyperthyroidism.
The condition is usually discovered in women between ages 40 and 60. Many people have no symptoms at all and only learn about it when a doctor finds an ovarian mass during routine imaging. Blood tests showing elevated T3 levels alongside other unusual patterns can point to this diagnosis before surgery.
Symptoms
- Pelvic or abdominal pain
- Abdominal bloating or swelling
- Feeling a mass in your lower belly
- Rapid heartbeat or heart palpitations
- Unexplained weight loss
- Nervousness or anxiety
- Increased sweating
- Tremors in your hands
- Difficulty sleeping
- More frequent bowel movements
Many women with struma ovarii have no symptoms at all, especially when the tumor is small. Symptoms of excess thyroid hormone only appear in about 5 to 8% of cases, when the thyroid tissue is actively producing hormones. Some people only discover the condition during surgery for other reasons or during routine pelvic exams.
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Causes and risk factors
Struma ovarii develops from germ cells in the ovary that are meant to become eggs. During development, these cells can mistakenly form different types of tissue, including thyroid tissue. The exact reason why this happens remains unclear. These growths are classified as teratomas, which are tumors that contain tissues from different parts of the body. When the teratoma is made up mostly of thyroid tissue, it becomes struma ovarii.
Risk factors for struma ovarii are not well understood because the condition is so rare. Most cases occur in women of reproductive age or in perimenopause. There is no strong evidence linking lifestyle factors, diet, or family history to this condition. The tumor typically grows slowly over time. When the thyroid tissue becomes functional, it starts producing hormones independently from your thyroid gland.
How it's diagnosed
Doctors diagnose struma ovarii through a combination of imaging studies and blood tests. An ultrasound or CT scan may show an ovarian mass with unusual characteristics. Blood tests can reveal elevated triiodothyronine, or T3 levels, while thyroid stimulating hormone, known as TSH, is suppressed. A thyroid uptake scan may show low uptake in the neck, suggesting hormone production is happening somewhere else in the body.
Rite Aid offers testing for T3 levels through our flagship blood panel. Testing can help identify unusual thyroid hormone patterns that might indicate struma ovarii. The final diagnosis usually requires surgical removal and examination of the tumor tissue under a microscope. This confirms the presence of thyroid tissue in the ovary.
Treatment options
- Surgical removal of the affected ovary and tumor, which is the primary treatment
- Monitoring thyroid hormone levels before and after surgery
- Beta blockers to control heart rate and anxiety if thyroid hormone levels are high
- Antithyroid medications to reduce hormone production before surgery in some cases
- Total thyroidectomy followed by radioactive iodine if cancer is present
- Regular follow-up imaging to watch for recurrence
- Thyroid hormone replacement if both ovaries or thyroid gland are removed
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Frequently asked questions
Struma ovarii is a rare type of ovarian tumor that contains thyroid tissue. This tissue can produce thyroid hormones even though it grows in the ovary instead of the thyroid gland. Most cases are benign, but about 5% can become cancerous.
Many women have no symptoms at all. When symptoms do occur, they may include pelvic pain, abdominal bloating, or a noticeable mass in the lower belly. If the tumor produces excess thyroid hormone, symptoms like rapid heartbeat, weight loss, anxiety, and increased sweating can develop.
Doctors typically find struma ovarii through pelvic imaging like ultrasound or CT scan showing an ovarian mass. Blood tests may reveal elevated T3 levels with suppressed TSH. A thyroid uptake scan can show low uptake in the neck, suggesting hormone production elsewhere in the body.
Blood tests alone cannot confirm struma ovarii, but they can provide important clues. Elevated T3 levels combined with suppressed TSH and low thyroid uptake suggest hormone production outside the thyroid. The final diagnosis requires surgical removal and microscopic examination of the tumor tissue.
Most cases of struma ovarii are benign, meaning not cancerous. However, about 5% of cases can be malignant or cancerous. Doctors determine this by examining the removed tumor tissue under a microscope after surgery.
The primary treatment is surgical removal of the affected ovary and tumor. If thyroid hormone levels are very high before surgery, doctors may prescribe beta blockers or antithyroid medications. If cancer is present, additional treatment may include removal of the thyroid gland and radioactive iodine therapy.
Struma ovarii can affect fertility if it causes significant ovarian enlargement or if surgical treatment requires removal of one or both ovaries. However, if only one ovary is removed and the other remains healthy, many women can still conceive naturally.
Struma ovarii is very rare, so specific risk factors are not well understood. It most commonly occurs in women between ages 40 and 60. There is no strong evidence linking lifestyle, diet, or family history to this condition.
Many people do not need thyroid medication after removal if their thyroid gland remains intact and functional. However, if both ovaries are removed or if you also need thyroid gland removal due to cancer, you will likely need thyroid hormone replacement for life.
Recurrence is rare after complete surgical removal of the tumor. Your doctor will recommend regular follow-up appointments and imaging studies to monitor for any signs of recurrence. Blood tests checking thyroid hormone levels are also part of ongoing monitoring.