A 56-year-old male presents to his doctor. Chief complaints include extended periods of heart palpitations, weight loss, and pain on the left side of his neck and throat.
Tests ordered included a thyroid function profile.
- TSH: 15.0 µIU/mL (ref range 0.4 - 4.12 µIU/mL) H
- FT3: 7.8 pg/mL (ref range 2.5 - 3.9 pg/mL) H
- FT4: 1.9 ng/dL (ref range 0.6 - 1.3 ng/dL) H
- TPOAb: <1.0 IU/mL(ref range <9.0 IU/mL)
- TgAb: <0.5 IU/mL (ref range <4.0 IU/mL)
In this case, the TSH level is found to be 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, the hyperthyroidism is said to be SECONDARY, or caused by a source other than the thyroid. In this case, a TSH-secreting tumor in the pituitary was discovered. Upon successful removal of the benign pituitary tumor, TSH levels returned to normal, as did the levels of thyroid hormones.