Patient history:
A 56-year-old presents to their physician. Chief complaints include extended periods of heart palpitations, weight loss, and pain on the left side of the neck and throat.
Tests ordered included a thyroid function profile.
Laboratory results:
| Test | Patient Result | Reference Range |
| TSH | 15.0 µIU/mL | 0.4 - 4.12 µIU/mL |
| FT3 | 7.8 pg/mL | 2.5 - 3.9 pg/mL |
| FT4 | 1.9 ng/dL | 0.6 - 1.3 ng/dL |
| TPOAb | <1.0 IU/mL | <9.0 IU/mL |
| TgAb | <0.5 IU/mL | <4.0 IU/mL |
In this case, the TSH level is highly elevated, as are the FT3 and FT4 levels. With excessive production of thyroid hormones, one would suspect that the negative feedback would signal the pituitary to stop producing TSH, but TSH levels persist at very high levels of activity. Thus, hyperthyroidism is considered SECONDARY or caused by a source other than the thyroid. In this case, a TSH-secreting tumor in the pituitary was discovered. After successfully removing the benign pituitary tumor, TSH levels returned to normal, as did the levels of thyroid hormones.
