What is the significance of a low Thyroid-Stimulating Hormone (TSH) level and an elevated Cancer Antigen 125 (CA-125) level?

From the Guidelines

Low TSH and elevated CA-125 are two separate laboratory findings that require immediate medical evaluation to rule out potential life-threatening conditions such as hyperthyroidism and ovarian cancer. The patient's low TSH level suggests possible hyperthyroidism, which may cause symptoms like weight loss, anxiety, rapid heartbeat, and heat intolerance, and typically requires endocrinology consultation and possibly medications such as methimazole (starting at 5-10 mg daily) or propranolol (10-40 mg three times daily) for symptom management 1. Meanwhile, the elevated CA-125 is a tumor marker often associated with ovarian cancer, but it can also increase with benign conditions like endometriosis, fibroids, or pelvic inflammatory disease, and warrants gynecological evaluation, possibly including transvaginal ultrasound and pelvic examination 1. Some key points to consider in the evaluation of elevated CA-125 include:

• CA-125 can be elevated in non-gynaecological malignancies and benign conditions, such as endometriosis and ovarian cysts 1
• Measuring serum carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 levels in addition to CA-125 may help distinguish primary mucinous ovarian tumours from a gastrointestinal metastasis 1
• Initial imaging should comprise pelvic ultrasound (US; transabdominal and/or transvaginal) and computed tomography (CT) of the thorax, abdomen and pelvis to complete clinical staging and aid surgical planning 1 It's essential to seek prompt medical attention for proper diagnosis and treatment of both conditions, as addressing only one might miss important health concerns, and the specific treatment approach will depend on the underlying causes identified through additional testing. Given the most recent and highest quality study available 1, a comprehensive evaluation including detailed history, clinical examination, serum CA-125, and imaging studies such as transvaginal ultrasound and CT scan is recommended to determine the underlying cause of the elevated CA-125 and to rule out ovarian cancer.

From the Research

Low TSH and Elevated CA-125

• Low TSH (thyroid-stimulating hormone) levels can indicate hyperthyroidism, a condition where the thyroid gland produces excess thyroid hormones 2, 3.
• Hyperthyroidism can be caused by various factors, including Graves' disease, toxic multinodular goiter, and toxic adenoma 2, 3.
• Elevated CA-125 levels are often associated with ovarian cancer, but can also be seen in other conditions, such as ascites caused by hypothyroidism 4.
• In some cases, hypothyroidism can cause ascites, which may lead to elevated CA-125 levels 4.
• Treatment of hyperthyroidism depends on the underlying cause and may involve antithyroid medications, radioactive iodine ablation, or surgery 2, 3.
• Thyroid hormone replacement therapy may be effective in resolving ascites and reducing CA-125 levels in cases of hypothyroidism 4.

Possible Causes and Treatments

• Hyperthyroidism:
  • Causes: Graves' disease, toxic multinodular goiter, toxic adenoma 2, 3
  • Treatments: antithyroid medications, radioactive iodine ablation, surgery 2, 3
• Hypothyroidism:
  • Causes: thyroid hormone deficiency 5, 6
  • Treatments: thyroid hormone replacement therapy 4
• Ascites with elevated CA-125:
  • Cause: hypothyroidism 4
  • Treatment: thyroid hormone replacement therapy 4

Diagnostic Considerations

• Thyroid function tests (TSH, free T4, free T3) can help diagnose hyperthyroidism or hypothyroidism 2, 3, 5, 6.
• CA-125 levels can be elevated in various conditions, including ovarian cancer and ascites caused by hypothyroidism 4.
• Thyroid scintigraphy may be recommended to establish the etiology of hyperthyroidism 2.