AssessmentsPituitary adenomas and pituitary hyperfunction: Clinical practice
USMLE® Step 2 style questions USMLE
A 48-year-old man comes to his outpatient provider because of headaches and changes in vision, which started two-months ago. The headaches are worse in the morning. Past medical history is notable for Cushing syndrome refractory to medical treatment, for which the patient underwent a bilateral adrenalectomy seven-months ago. He was prescribed hydrocortisone supplements after the surgery but has been inconsistent in taking them. In the office, his temperature is 37.2°C (99.0°F), pulse is 75/min, respirations are 20/min, and blood pressure is 115/77 mmHg. Physical exam shows hyperpigmentation of the skin. Visual field testing reveals bitemporal hemianopsia. Which of the following is the next best step in the diagnosis of this patient?
Content Reviewers:Rishi Desai, MD, MPH
One group of cells are the somatotrophs which secrete growth hormone, or GH.
Then, there are the corticotrophs, and they secrete adrenocorticotropic hormone, or ACTH for short.
There are also thyrotrophs which secrete thyroid stimulating hormone, or TSH.
On an unenhanced MRI, meaning, without contrast, normal pituitary tissue has a greater signal intensity than brain tissue - so it looks whiter.
A pituitary adenoma, on the other hand, has a signal that is similar to surrounding brain tissue - so it’s “just as grey” instead.
Following administration of Gadolinium as contrast, normal pituitary tissue lights up like a christmas tree.
An adenoma typically takes in more contrast than the central nervous system, but less than the healthy part of the pituitary - so grey-wise, it’s somewhere in between the two.
The MRI helps ascertain the size of the tumor - pituitary adenomas smaller than 1 centimeter are called microadenomas, whereas those larger than 1 centimeter are called macroadenomas.
Both micro and macroadenomas can be functional, meaning that they secrete hormones, or non-functional, meaning they don’t - so any individual with a confirmed pituitary adenoma should be screened for hormone hypersecretion.
With excess prolactin, females have symptoms of hypogonadism, like infertility, oligomenorrhea or amenorrhea, as well as galactorrhea - which is a milky nipple discharge outside of pregnancy or breastfeeding.
Serum prolactin levels higher than 200 nanograms per milliliter confirm the diagnosis, and treatment relies on dopamine agonists like cabergoline, that inhibit prolactin secretion just like dopamine would.
Excess growth hormone causes different symptoms in children versus adults.
In adults, it causes acromegaly, which is where there’s enlargement of the bones of the skull, hands and feet.
See, daily growth hormone secretion is pulsatile, sometimes more and sometimes less. However, the mean concentrations of growth hormone are sufficient to make the liver release a constant amount of IGF-1 throughout the day, so IGF-1 levels are a better estimate of growth hormone secretion - with high levels suggesting growth hormone hypersecretion.
If there are high IGF-1 levels, serum growth hormone is measured to confirm the diagnosis.
Specifically, serum growth hormone is measured before and two hours after giving an individual 75 grams of glucose dissolved in a bit of water. Normally, serum growth hormone two hours after ingesting glucose is less than 1 nanogram per milliliter, but if there’s growth hormone hypersecretion, the level is higher than 1 nanogram per milliliter.
Treatment is usually surgical, through transsphenoidal resection.
Pituitary adenomas are benign tumors that develop in the anterior pituitary gland that's located at the base of the brain. These tumors can cause the pituitary gland to produce too much of one or more hormones, leading to pituitary hyperfunction.
Symptoms depend on the specific hormones involved, though other symptoms might be due to the mass effect of these tumors. Treatment for pituitary adenomas may include medications to shrink the tumor and control hormone levels; surgery to remove the tumor; or radiation therapy to shrink it.