What does Low Cortisol but normal ACTH mean for a pituitary tumor?

[wheresmyjava]

I have a microadenoma measuring 7.5mm x 8.5mm. It has tripled to this size in the last two hears. I have frequent headaches, extreme fatigue which are my two worst symptoms. My endo tested my cortisol which was low. I later had an ACTH test which had normal results.

What does this mean? Does it mean that my tumor is not causing my low cortisol or my extreme fatigue? What should I look into next to try and find a cause of my exhaustion?

[dr_simran]

Hello wheresmyjava,

Microadenoma is a tumor less than 10 mm in diameter. Pituitary adenomas may secrete hormones, or they may be clinically inactive. Many pituitary lesions are discovered while investigating other neurologic problems; these are called incidentalomas. Prognosis depends on the hormonal activity of the adenoma. Most incidentalomas are inactive and do not cause morbidity, except morbidity related to excessive investigation. Autonomous secretion by a tumor usually shows an inappropriate relationship between the level of the hormone secreted by the peripheral gland and the stimulating pituitary hormone (ACTH). For example, a patient with Cushing disease, who will have an elevated or normal ACTH level.

Refer: http://www.emedicine.com/MED/topic2973.htm

Best