Sub-Sternal Thyroids and Goiters
Thyroids which grow into the chest to cause problems
Please read the page on thyroid goiters before you read this page. It will make it easier to understand. The normal thyroid gland resides in the neck, with both lobes wrapping gently around the trachea (breathing tube).
The normal thyroid gland resides in the neck, with both lobes wrapping gently around the trachea (breathing tube). When thyroids get enlarged (called a goiter), they can grow a number of different directions. Usually, they will grow within the neck as shown in the picture of the woman on our goiter page. When this is the case, they are seen as a large mass in the neck. Since they grow slowly, taking a number of years to obtain their large size, many people aren't aware of just how large the thyroid has become.
Less commonly, a thyroid will grow downward rather than up and out within the neck. When this happens, the thyroid will grow down the trachea into the chest. This can become an even bigger problem since the chest is surrounded by a very rigid bone structure (the chest cavity). The top of the chest cavity is made up of the spinal column in the back, the first and second ribs on the sides, and the collar bones (clavicles) and breast bone (sternum) in the front. When a thyroid gets enlarged within this rigid bony structure, it will compress those structures which are soft such as the trachea, lungs, and blood vessels (the bones will not give way). This is what makes sub-sternal thyroids a special case which deserve special attention.
This chest x-ray shows a sub-sternal thyroid which is compressing and displacing the trachea to the patient's left The trachea (outlined in light yellow) should run straight from the mouth/nose down to the lungs rather than being curved like it is in this picture. This is not as un-common as you may think.
The picture on the left shows a CT scan (also called CAT scan) from the same patient. The CT produces a picture as if the patient was cut in half so we can see inside. The patient is lying on her back and this is a cut through the upper chest just above the heart. The two large black areas are the lungs and are labeled with an "L". The sternum (breast bone) is the white curved structure near the top of the picture. The trachea (outlined in red) should be in the midline, but is pushed to the left and compressed by a large amount of thyroid tissue (outlined in yellow) which is extending down into the chest. You can see that some of the space which would normally be taken up by the right lung is replaced with the mass (loss of lung volume). Remember, x-rays usually show the patient's right on the left of the picture as if we were looking at the patient. Compression of the trachea and esophagus (hard to see on x-rays) by the large thyroid are what gives the symptoms listed below. This can happen with a goiter which is completely in the neck, or it can happen if the goiter grows down into the chest (remember, it doesn't belong in the chest!).
This CT scan shows a similar problem. The thyroid goiter (outlined in yellow) has grown into the chest below the sternum. The trachea (outlined in red) is displaced to the patient's right side (shown on CT scans on the left of the picture). Remember, the trachea is supposed to be in the middle of the chest and the thyroid should not extend into the chest at all. This patient has a hard time swallowing breads and meats, and she feels like she is suffocating when she lies on her back.
Symptoms of Sub-Sternal Thyroids
- Frequent coughing
- Feeling that "something is stuck in my throat"
- Food getting stuck in the upper esophagus when swallowing (breads and meats most commonly)
- Waking up at night feeling that you can't breathe
- Inability to lay down or sleep on your back because of symptoms above (when it was never a problem before)
Treatment of Sub-Sternal Thyroids
It is a misconception that all sub-sternal thyroids require that the sternum be split to allow it to be removed. In fact, this is extremely rare. Essentially all sub-sternal thyroids can be removed through a conventional thyroid neck incision. It must be remembered that the blood supply to the thyroid is from two separate sources both of which arise in the neck (and not the chest). That means that the blood supply can be cut off from above without undue fear of intra-operative bleeding. After the patient is put to sleep under anesthesia, his/her neck can be extended fairly far backward which helps pull the thyroid up from the chest making it easier to remove. Remember, even though these goiters can extend WAY down into the chest, it is very uncommon for a sternal splitting operation to be necessary.