Two ways a pituitary tumor causes harm
A pituitary adenoma is a benign growth of pituitary cells. It causes trouble in two distinct ways, and most clinical pictures are a mix of the two. First, by secreting too much of one hormone if the tumor cells happen to be hormone-makers — this is hormone excess. Second, by taking up space: as the lump grows in its tight bony pocket, it crushes the normal gland around it and presses on nearby structures, causing hormone deficiency of the others and sometimes vision loss as it squeezes the optic nerves overhead.
Too much growth hormone: acromegaly
When an adenoma over-makes growth hormone, the effects depend on age. In an adult whose long bones have stopped growing, the body cannot get taller, so it grows *outward and thicker*: this is acromegaly — enlarging hands and feet, a coarsening face, an enlarging jaw and tongue, joint pain, and metabolic problems. In a child whose growth plates are still open, the same excess produces extreme height instead — gigantism. Same hormone, different timing, different shape.
Much of growth hormone's effect is carried out by IGF-1, made by the liver in response to GH. Because GH is released in pulses and rises and falls during the day, a single GH measurement is unreliable — but IGF-1 stays steadier and reflects the day's overall GH activity. This is why IGF-1 is the practical screening test for acromegaly. One common treatment is a somatostatin analog — a drug that mimics the hypothalamus's own GH brake from guide 3, turning down the tumor's output.
Too little of everything: hypopituitarism
The opposite failure is hypopituitarism — the pituitary makes too little of its hormones, from a large tumor, surgery, radiation, severe bleeding around childbirth, or injury to the stalk. Because the pituitary commands several axes at once, losing it tends to dim many systems together: low ACTH starves the adrenals of the cortisol signal, low TSH slows the thyroid, low LH and FSH shut down the gonads, and low GH saps energy and body composition. The pattern is broad and quiet rather than dramatic, which is part of why it is easy to miss.
- Confirm the pattern: measure each pituitary order *together* with the gland hormone it controls — low-and-low points to the pituitary, just as the feedback logic from guide 4 predicts.
- Replace what is missing, gland by gland, using hormone replacement therapy — the downstream hormones (e.g. cortisol, thyroid hormone, sex steroids), not the pituitary signals.
- Treat the cortisol axis first and most carefully: a missing stress response is the part of hypopituitarism that can become life-threatening.