Pituitary adenoma
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Pituitary adenoma
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| Laboratory value | Result |
| Sodium | 146 mmol/L |
| Potassium | 3.9 mmol/L |
| Bicarbonate | 26 mmol/L |
| Fasting glucose | 137 mg/dL |
| 24-hour urine cortisol* | 72 µg/day |
| Serum ACTH** | 35 pg/mL |
*Normal range: 4-40 µg/day
**Normal range: 5-20 pg/mL
The serum cortisol levels are significantly reduced in response to a high-dose of dexamethasone. Which of the following is the most likely underlying pathophysiology for this patient’s condition?
Memory Anchors and Partner Content
External References
First Aid
2024
2023
2022
2021
Amenorrhea
pituitary adenoma and p. 540
Bitemporal hemianopia p. 557
pituitary adenoma p. 540
Headache p. 532
pituitary adenomas and p. 342, NaN
Pituitary adenoma p. 540
Pituitary adenomas
acromegaly and p. 341
GH and p. 338
goiter and p. 346
hypopituitarism and p. 349
Pituitary tumors
diabetes insipidus p. 342
MEN 1 and p. 356
Transcript
Pituitary adenoma can be broken down - “adeno” refers to a gland and “oma” refers to a tumor, so pituitary adenoma is a tumor that develops in the hormone-producing cells of the pituitary gland.
Normally, the pituitary is a pea-sized gland, hanging by a stalk from the base of the brain.
It sits just behind the eyes near the optic chiasm, which is where the optic nerves cross.
The anterior pituitary, which is the front of the pituitary gland, contains a few different types of cells, each of which secretes a different hormone.
The largest group of cells are the somatotropes which secrete growth hormone, or GH for short, which goes on to promote tissue and organ growth.
The second largest cell group are the corticotrophs which secrete adrenocorticotropic hormone, or ACTH for short.
ACTH stimulates the adrenal glands to secrete cortisol, a hormone that controls the stress response and metabolic regulation.
A smaller cell group are the lactotrophs which secrete prolactin.
Prolactin stimulates breast milk production, and also inhibits ovulation, which is when an egg cell is released from the ovary, and inhibits spermatogenesis, which is the development of sperm cells.
There are also thyrotrophs which are cells that secrete thyroid stimulating hormone, or TSH which goes on to stimulate the thyroid gland.
And finally, there are also gonadotrophs which secrete two gonadotropic hormones - luteinizing hormone, or LH, and follicle-stimulating hormone, or FSH, both of which go on to stimulate the ovaries or testes.
In pituitary adenomas, one of these cells mutates and becomes neoplastic, meaning that it starts dividing uncontrollably and over time it forms a tumor.
Summary
Pituitary adenomas are benign tumors that occur in the pituitary gland. They vary depending on their size and the type of hormones they produce. Some pituitary adenomas do not produce any hormones and are referred to as non-functioning adenomas, while others produce hormones that can cause a wide range of symptoms.
Common symptoms include headaches, visual disturbances, fatigue, and changes in sexual function or menstrual cycles. The most common types involve lactotrophs that make prolactin, somatotrophs that make growth hormones, and corticotrophs that make ACTH. They are usually diagnosed by checking hormone levels and obtaining an MRI and are treated with medications or surgery.
Sources
- "Robbins Basic Pathology" Elsevier (2017)
- "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
- "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
- "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
- "Harrison's Endocrinology, 4E" McGraw-Hill Education / Medical (2016)
- "Management of hormone-secreting pituitary adenomas" Neuro-Oncology (2016)
- "The prevalence of pituitary adenomas" Cancer (2004)
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