Pituitary adenoma

Definitions & Key takeaways

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.

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Introduction0:00–0:16

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.

Physiology0:16–1:45

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.

Pathology1:45–3:08

But these cells don’t invade neighboring tissues, so this is considered a benign tumor rather than a malignant one. Pituitary adenomas can be classified by their size, adenomas smaller than 1cm are called microadenomas, and those larger than 1cm are called macroadenomas.
Macroadenomas are more likely to compress surrounding structures like the meninges, which is the protective layer overlying the brain that typically causes pain when it’s stretched.
Macroadenomas can also compress optic nerves as they cross at the optic chiasm. That can affect a person’s ability to view things that are in the temporal visual field of both eyes, also called “bitemporal hemianopia”.
Finally, the compression can also affect other healthy pituitary cells and interfere with their ability to make hormones.Pituitary adenomas that secrete hormones are called functional adenomas, whereas those that don’t are called non-functional adenomas.
Functional pituitary adenomas are divided into a few different types depending on the cells that they arise from and the hormone these cells produce.

Signs and symptoms3:08–6:05

The most common type of pituitary adenoma is a prolactinoma which arises from lactotrophs that make prolactin. In women, excess prolactin causes amenorrhea, which is when there is loss of menstrual bleeding and galactorrhea, which is a milky nipple discharge.
In men, excess prolactin causes a low libido - a low sex drive and gynecomastia or breast enlargement. The second most common type of pituitary adenoma arises from somatotropes that make growth hormone.
In children, who haven’t had fusion of their epiphyseal plates, which are the parts near the ends of the long bones where new bone growth takes place, this type of adenoma causes gigantism.
In gigantism, there is an increase in body size and height with disproportionately long limbs. In adults, who have had their growth plates close, this type of adenoma causes acromegaly.
In acromegaly, there is enlargement of the bones of the skull, hands and feet. In both gigantism and acromegaly, excess growth hormone causes enlargement of visceral organs, like the heart.
In fact, a serious complication of growth hormone secreting adenomas is heart failure, due to an enlarged heart that has very little room within it for the blood.
The third most common type of pituitary adenoma is an adrenocorticotropic hormone secreting tumor which arises from corticotrophs that make adrenocorticotropic hormone.
The excess adrenocorticotropic hormone stimulates the adrenal glands to make excess cortisol, leading to Cushing syndrome.
Cushing syndrome can result from a number of causes, and when it develops due to a pituitary adenoma, it’s specifically called Cushing disease.
Cushing disease causes a variety of symptoms including a change in fat distribution - creating moon facies - a round, full moon shaped face, a buffalo hump - a fatty hump on the upper back, and truncal obesity - where fat gathers around the abdomen and trunk rather than in the limbs.
Finally, there can be adenomas that develop from thyrotrophs and gonadotrophs. Thyrotroph derived adenomas are quite rare, but they can cause excess TSH and, as a consequence, signs and symptoms of hyperthyroidism.
These include weight loss despite an increased appetite, heat intolerance, sweating, insomnia, agitation and tremor. Finally, gonadotroph derived adenomas rarely secrete hormones, so they’re usually clinically silent.
In fact, they’re the most frequent subtype of non-functional tumors. If they grow big enough, they might cause compression signs, like headache and visual impairment.Diagnosis of pituitary adenomas is based on measuring pituitary hormone levels, and then obtaining an MRI to image the pituitary gland to see if there’s a tumor and estimate its size.The treatment for a pituitary adenoma, depending on the type and size.

Diagnosis6:05–6:18

Treatment6:18–6:53

When dealing with hormone-producing pituitary adenomas, prolactinomas are usually treated successfully with medication and rarely require surgical removal or radiation therapy, while somatotrophic and corticotrophic adenomas usually require a transsphenoidal surgical resection, which is when the tumor is removed through the nose and the sphenoidal sinus.
When dealing with non-functional pituitary adenomas, only tumors large enough to cause symptoms through compression require surgery.All right, as a quick recap, pituitary adenomas are benign tumors of anterior pituitary cells and their symptoms depend on their size and cellular origin.

Review6:53–7:20

The most common types involve lactotrophs that make prolactin, somatotropes that make growth hormone, and corticotrophs that make ACTH.
They are usually diagnosed by checking hormone levels and obtaining an MRI, and are treated with medications or surgery.