1. Final Diagnosis: Panhypopituitarism and macroprolactinoma

2. What is your management plan ?

Hormone replacement and cabergoline

3. Which hormone are you going to replace first and why?

Hydrocortisone first to avoid precipitating adrenal crisis.

4. Which hormone are you going to replace next?

After cortisol, replace levothyroxine

5. Which hormone is third?

Testosterone after checking PSA, screen for sleep apnea and while watching for polycythemia

6. How do you treat his pituitary tumor?

Medically, since it is a prolactinoma

7. How do you know that this is a prolactinoma and not a large non secreting adenoma causing panhypopituitarism and prolactin elevation due to hypothalamic/pituitary stalk compression?

Prolactin level correlates with adenoma size. This macroadenoma has a level > 2000. A non secreting adenoma elevating prolactin by stalk compression would have elevated prolactin typically to < 100.

8. Despite very low cortisol level, why are his electrolytes correcting to normal and why is the potassium normal?

Adrenal mineralocorticoid production is under the control of Renin/angiotensin axis and not under pituitary. In primary adrenal failure, there is hyponatremia and hyperkalemia

Lessons to learn:

1. In endocrine, biochemical testing ALWAYS comes before imaging. If imaging finds an incidentaloma, check biochemistry always.

2. A pituitary hormone level may be normal range, but it always must be interpreted along with its target hormone. He has secondary hypothyroidism and secondary hypogonadism as his TSH and LH/FSH are normal despite very low T4 and testosterone. If pituitary is normal, the levels would have been high when there is low T4 and low testosterone.

3. In cases of pituitary tumors, usually hormones are lost in the order of most important to least important (Go (GH) Look (LH) For (FSH) That (TSH) Adenoma (ACTH). If there is secondary hypothyroidism, always check for cortisol/ACTH axis before starting levothyroxine to avoid precipitating adrenal crisis.

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