Ninety percent of ectopic thyroids are located in/on the?

Ectopic thyroid tissue is thyroid tissue that is located outside its usual anatomic location in the neck. The vast majority of ectopic thyroid cases, approximately 90%, are found on the lingual dorsum, which is the upper surface of the tongue. This occurrence can lead to the presence of thyroid tissue in an abnormal location, where the ectopic thyroid may be the only functioning thyroid tissue a person has, potentially leading to hypothyroidism if it is not adequate for the body's requirements.

In cases of hypothyroidism, if the ectopic thyroid is the sole source of thyroid hormone, the patient may experience symptoms related to insufficient hormone production, including fatigue, weight gain, and sensitivity to cold. Conversely, hyperthyroidism would typically indicate an overproduction of thyroid hormones, which is less common in ectopic thyroid situations, especially when the ectopic tissue is the only functioning thyroid tissue present.

Thus, the association of ectopic thyroid tissue on the lingual dorsum with hypothyroidism accurately reflects the prevalence and nature of these cases, making it the correct answer to the question.