PANCE Blueprint Endocrinology (7%)

Pituitary adenoma and neoplasm (Lecture)

Patient will present as → a 31-year-old woman who complains of irregular, infrequent menstrual periods. On further questioning, she complains of headaches, fatigue, and breast discharge. She takes ibuprofen only occasionally. The serum prolactin level is 380 μg per L.

Pituitary adenomas are benign tumors of the anterior pituitary that derive from one of the five types of pituitary hormone-producing cells

  • Common presentations associated with pituitary adenoma (may involve multiple endocrine abnormalities)
  • Pituitary adenomas < 1 centimeter are called microadenomas, whereas those > 1 centimeter are called macroadenomas
Classification of Pituitary Adenomas
Tumor Type Secretory Product(s) Relative Frequency (%)
Prolactinoma (Galactorrhea)

  • Women present with amenorrhea, galactorrhea, infertility, decreased libido
↑ Prolactin 50
Somatotroph adenoma (acromegaly & gigantism) ↑ Growth Hormone (GH) 10
Corticotroph adenoma (Cushing's disease) ↑ ACTH 5
Thyrotroph adenoma (Hyperthyroidism) ↑ TSH 1
Gonadotroph adenoma ↑ LH ↑ FSH 3
Non-Secreting Adenoma α alpha -subunit 34

1810 Major Pituitary Hormones

Diagnosis is made by MRI - look for sellar lesions/tumors

  • Endocrine studies: Prolactin, GH, ACTH, TSH, FSH, LH

Treatment is often surgical

  • Transsphenoidal surgery: management of choice for removal of ACTIVE or compressive tumors
  • Medical management is the first line for prolactinomas - Dopamine inhibits prolactin release - Cabergoline or Bromocriptine (dopamine agonists)
    • A dopamine agonist drug should usually be the first treatment for patients with hyperprolactinemia of any cause, including lactotroph adenomas (prolactinomas) of all sizes. These drugs decrease serum prolactin concentrations and decrease the size of most lactotroph adenomas. Following the decrease in serum prolactin and adenoma size in patients with macroadenomas, visual and pituitary function often return to normal.
    • Transsphenoidal surgery is considered only when dopamine agonist treatment has been unsuccessful or in specific situations, such as a giant lactotroph adenoma in a woman wishing to become pregnant.
  • Acromegaly: TSS + Bromocriptine (dopamine decreases GH production)

osmosis Osmosis


Prolactinoma is a prolactin secreting tumor of the pituitary gland. This tumor is the most common adenoma of the pituitary gland. These tumors are benign but can cause symptoms due to elevated prolactin levels in the blood or by compression of nearby structures. Prolactin is the hormone that stimulates the breast to produce breast milk. Therefore, elevated prolactin levels are usually seen during pregnancy and after childbirth. Pathologic secretion of prolactin from prolactinomas can cause galactorrhea in women although rare in men because of insufficient breast tissue. Prolactin also inhibits the release of gonadotropin releasing hormone. Normally, GnRH stimulates the release of FSH and LH from the anterior pituitary, which plays an important role in the synthesis of sex hormones. Increased prolactin can therefore cause decreased levels of sex hormone in men and women, leading to impotence and amenorrhea, respectively. Enlargement of the tumor can lead to compression of the optic chiasm resulting in bitemporal hemianopia. Dopamine physiologically suppresses prolactin secretion and is used in the treatment of prolactinomas.

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Question 1
A 25-year-old woman visits your office with a complaint of spontaneous nipple discharge and irregular menstrual cycles for the past eight months. She also notes a decreased libido. Physical examination confirms galactorrhea. Her blood pressure is 130/85 mmHg. She denies significant weight changes or excessive stress. What is the most likely diagnosis?
While hypothyroidism can cause menstrual irregularities and elevated prolactin levels, it is less likely to present with galactorrhea and does not typically cause decreased libido as a primary symptom.
Polycystic ovary syndrome (PCOS)
PCOS can cause menstrual irregularities and sometimes galactorrhea, but it is often associated with other symptoms like hirsutism, acne, and obesity, which are not mentioned in this case.
Pregnancy is a common cause of amenorrhea and galactorrhea, but should be easily ruled out with a pregnancy test.
Medication side effect
Certain medications, particularly antipsychotics and antidepressants, can cause hyperprolactinemia and galactorrhea. However, there is no mention of medication use in this patient's history.
Question 1 Explanation: 
The patient's symptoms of galactorrhea, amenorrhea, and decreased libido, along with the absence of other systemic symptoms, are highly suggestive of a prolactinoma. Prolactinomas are benign pituitary tumors that secrete prolactin, leading to hyperprolactinemia, which can cause galactorrhea and menstrual irregularities. This is the most likely diagnosis given the clinical presentation.
Question 2
A 45-year-old male presents with headaches, visual disturbances, and recent onset of fatigue. He reports a loss of peripheral vision. Physical examination reveals bitemporal hemianopsia. Which of the following is the most appropriate initial diagnostic test to evaluate for a suspected pituitary adenoma?
Serum prolactin level
While elevated prolactin can be indicative of a prolactinoma, a type of pituitary adenoma, it is not the initial diagnostic test for a suspected pituitary adenoma, especially in the presence of visual symptoms.
MRI of the brain with focus on the sella turcica
CT scan of the head
A CT scan is less sensitive than MRI for detecting pituitary adenomas and does not provide as detailed an image of the sellar region.
Serum thyroid-stimulating hormone (TSH) and free thyroxine (T4) levels
These tests assess thyroid function and may be altered by a pituitary adenoma, but they are not initial diagnostic tests for a pituitary adenoma.
24-hour urine cortisol level
This test is used to diagnose Cushing's syndrome, which can be caused by a pituitary adenoma, but it is not the initial test for a suspected pituitary adenoma.
Question 2 Explanation: 
The patient's symptoms of headaches, visual disturbances, particularly bitemporal hemianopsia, and fatigue are suggestive of a pituitary adenoma, which can compress the optic chiasm. An MRI of the brain, with a focus on the sella turcica, is the most appropriate initial diagnostic test. MRI provides detailed images of the pituitary gland and surrounding structures, allowing for the identification and characterization of a pituitary adenoma.
Question 3
A 30-year-old woman is diagnosed with prolactinoma after presenting with amenorrhea and galactorrhea. MRI confirms a 1 cm pituitary adenoma. The patient does not desire pregnancy. Which of the following is the first-line treatment for this patient?
Transsphenoidal surgery
While surgery is an option for treating prolactinomas, it is generally reserved for patients who are intolerant to medical therapy or have a tumor that is compressing surrounding structures.
Radiation therapy
This is typically a third-line treatment for prolactinomas, used when medications and surgery are not effective or feasible.
High-dose corticosteroids
Corticosteroids are not used in the treatment of prolactinomas. They are used in the management of other conditions, such as adrenal insufficiency or certain brain tumors, but not for prolactinomas.
Although bromocriptine is a dopamine agonist used in the treatment of prolactinomas, it is generally considered second-line due to a less favorable side-effect profile compared to cabergoline.
Question 3 Explanation: 
Cabergoline, a dopamine agonist, is the first-line treatment for prolactinomas. It is preferred over other treatments due to its higher efficacy and lower side-effect profile compared to other dopamine agonists like bromocriptine. Cabergoline effectively reduces prolactin levels, shrinks the tumor size, and restores normal menstrual function and fertility in most patients.
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References: Merck Manual · UpToDate

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