Pituitary tumors are quite common. Studies on autopsies suggest that about 20 percent of people have a pituitary tumor that would probably not have been discovered during their lifetime. MRI studies suggest that a pituitary tumor occur in between 5 percent and 10 percent of people. When a pituitary tumor is found on MRI when the test is ordered for another indication, it is called an “incidentaloma” and has been thought to be a clinically insignificant lesion. However, Dr. Friedman published a paper in Clinical Endocrinology that found that although these tumors are benign, they may affect the secretion of other pituitary hormones. This is most likely due to the tumors affecting the blood flow to the normal pituitary cells. There is a defined order of pituitary hormone secretion that is affected with damage to the pituitary:
3-sex hormones (estrogen and testosterone)
4-only rarely is ACTH/cortisol
The order of decrease in hormone secretion is similar in most patients with pituitary tumors, in that growth hormone deficiency is the most common and ACTH/cortisol is the least common. While many endocrinologists would do tests looking for pituitary hormone deficiencies only if the patient had a known pituitary macroadenoma (tumor greater than 1 cm) or prior surgery or radiation of the pituitary, Dr. Friedman believes that hypopituitarism and pituitary dysfunction are underdiagnosed and need to be looked for. Therefore, if patients have signs and symptoms of hypopituitarism including growth hormone deficiency that include fatigue, poor sleep, muscle pain, joint pain, weight gain, depression, and sluggishness, Dr. Friedman would order pituitary hormone testing. If they then come back suggestive of hypopituitarism, which would include a low IGF-1 (a hormone called insulin-like growth factor which is a marker of growth hormone), or a low testosterone in both males and females, or what is called central hypothyroidism where you have a low free T4 and a low TSH, these would all be indications of pituitary dysfunction.