Type 3 Deiodinase Excess (Consumptive Hypothyroidism)
What is Type 3 Deiodinase Excess (Consumptive Hypothyroidism)?
Type 3 deiodinase excess is a rare form of hypothyroidism. It happens when your body breaks down thyroid hormones too quickly. An enzyme called type 3 deiodinase inactivates thyroid hormones before they can do their job.
This condition is also called consumptive hypothyroidism because thyroid hormones are consumed or used up too fast. Large hemangiomas, certain tumors, or liver disease can produce excessive amounts of this enzyme. Your thyroid gland may work normally, but the hormones get inactivated before reaching your cells.
The result is low levels of active thyroid hormones in your blood. This leads to hypothyroidism symptoms even though your thyroid gland itself is healthy. Blood tests show low free T3 and free T4 levels despite normal or elevated TSH.
Symptoms
- Fatigue and weakness that gets worse over time
- Weight gain despite normal eating habits
- Cold intolerance and feeling chilly often
- Dry skin and brittle hair
- Constipation and slow digestion
- Muscle aches and joint pain
- Slow heart rate
- Depression or brain fog
- Swelling in the face or legs
- Presence of a large hemangioma or tumor
Some people may have mild symptoms at first. Symptoms often develop gradually as more thyroid hormone gets inactivated. Infants with large hemangiomas may show signs early in life.
Concerned about Type 3 Deiodinase Excess (Consumptive Hypothyroidism)? Check your levels.
Screen for 1,200+ health conditions
Causes and risk factors
Type 3 deiodinase excess happens when tissues produce too much of the enzyme that breaks down thyroid hormones. Large infantile hemangiomas are the most common cause in babies and children. These benign blood vessel tumors can grow rapidly and produce massive amounts of the enzyme. Some liver cancers and other tumors also make excess type 3 deiodinase. Severe liver disease can impair thyroid hormone metabolism too.
Risk factors include having a large hemangioma, especially one bigger than 5 centimeters. Certain types of liver tumors increase risk as well. This condition is different from typical hypothyroidism because the thyroid gland works normally. The problem lies in how quickly hormones get inactivated in other tissues.
How it's diagnosed
Diagnosis starts with blood tests that measure thyroid hormone levels. Free T3 and free T4 tests show how much active thyroid hormone is in your blood. Rite Aid offers FT3 testing as part of our core panel to help detect thyroid hormone abnormalities. In type 3 deiodinase excess, both FT3 and FT4 are typically low. TSH levels may be normal or high as your body tries to compensate.
Your doctor will also look for underlying causes like hemangiomas or tumors. Imaging tests such as ultrasound or MRI can identify large hemangiomas. Measuring reverse T3 levels may also help since this inactive form increases when type 3 deiodinase is overactive. The pattern of low active hormones with a visible hemangioma or tumor strongly suggests this diagnosis.
Treatment options
- High-dose thyroid hormone replacement to overcome the rapid inactivation
- Treatment of the underlying hemangioma or tumor causing excess enzyme
- Propranolol medication to shrink infantile hemangiomas
- Surgical removal of hemangiomas when appropriate
- Laser therapy for accessible hemangiomas
- Cancer treatment if a tumor is the cause
- Regular monitoring of thyroid hormone levels
- Nutritional support with selenium and zinc for thyroid health
- Adequate protein intake to support hormone production
Concerned about Type 3 Deiodinase Excess (Consumptive Hypothyroidism)? Get tested at Rite Aid.
- Simple blood draw at your nearest lab
- Results in days, not weeks
- Share results with your doctor
Frequently asked questions
Type 3 deiodinase excess is a rare condition where your body breaks down thyroid hormones too quickly. An enzyme called type 3 deiodinase inactivates thyroid hormones before they can work properly. This causes hypothyroidism even though your thyroid gland functions normally.
The most common cause is large infantile hemangiomas, which are benign blood vessel tumors. These tumors produce excessive amounts of type 3 deiodinase enzyme. Certain liver cancers and severe liver disease can also cause this condition by increasing enzyme activity.
In regular hypothyroidism, your thyroid gland does not produce enough hormones. In type 3 deiodinase excess, your thyroid works fine but hormones get inactivated too quickly. The problem is with hormone breakdown in other tissues, not hormone production.
Symptoms include fatigue, weight gain, cold intolerance, dry skin, and constipation. You may also experience muscle aches, slow heart rate, and brain fog. Many people also have a visible hemangioma or tumor that causes the condition.
Blood tests measuring free T3 and free T4 levels are essential for diagnosis. Both levels are typically low in this condition. Your doctor will also look for underlying hemangiomas or tumors using imaging tests like ultrasound or MRI.
Yes, Rite Aid offers FT3 testing as part of our core panel. This test measures free T3 levels, which are typically low in consumptive hypothyroidism. Regular testing helps track your thyroid hormone levels and treatment response.
Treatment involves high-dose thyroid hormone replacement to overcome the rapid breakdown. Treating the underlying cause is also important. For infantile hemangiomas, propranolol medication can help shrink the tumor and reduce enzyme production.
It can be reversible if the underlying cause is treated successfully. When hemangiomas shrink or are removed, enzyme levels return to normal. Once the source of excess enzyme is gone, thyroid hormone levels often stabilize without lifelong treatment.
This is a very rare condition. It occurs most often in infants with large hemangiomas bigger than 5 centimeters. Adults can develop it from certain tumors or severe liver disease, but this is uncommon.
Untreated consumptive hypothyroidism can cause severe symptoms and developmental delays in children. Adults may experience worsening fatigue, weight gain, and mental slowness. The underlying hemangioma or tumor may also grow larger if not addressed.