20: Pituitary Flashcards
How is acromegaly diagnosed and what is the treatment?
Diagnosis: Elevated Insulin-like growth factor (IGF-1) is the best test, growth hormone > 10 (present in 90% of cases)
Treatment: Octreotide or transsphenoidal resection (XRT and bromocriptine can be used as secondary therapies)
[UpToDate: The best single test for the diagnosis of acromegaly is measurement of serum IGF-1. Unlike GH, serum IGF-1 concentrations do not vary from hour to hour according to food intake, exercise, or sleep, but instead reflect integrated GH secretion during the preceding day or longer. Serum IGF-1 concentrations are elevated in virtually all patients with acromegaly and provide excellent discrimination from normal individuals. A normal serum IGF-1 concentration is strong evidence that the patient does not have acromegaly.
Our approach, which is similar to that of the Endocrine Society, includes measurement of a serum insulin-like growth factor 1 (IGF-1) concentration as the first step. A normal serum IGF-1 concentration is strong evidence that the patient does not have acromegaly. If the serum IGF-1 concentration is high (or equivocal), serum GH should be measured after oral glucose administration. Inadequate suppression of GH after a glucose load confirms the diagnosis of acromegaly. Once the presence of excess GH secretion is confirmed, the next step is pituitary magnetic resonance imaging (MRI).
For patients with a microadenoma, a macroadenoma that appears to be fully resectable, or a macroadenoma threatening or impairing vision, we recommend transsphenoidal surgery performed by a neurosurgeon with considerable experience (Grade 1B).
For patients with an adenoma that does not appear to be fully resectable and for patients whose risk of surgery is great or who choose not to have surgery, we suggest primary therapy with a long-acting somatostatin analog (Grade 2B).
If transsphenoidal surgery results in normalization of serum insulin-like growth factor 1 (IGF-1) concentration, we suggest no further therapy (Grade 2B).
If transsphenoidal surgery does not normalize the serum IGF-1 concentration, we suggest therapy with a long-acting somatostatin analog (Grade 2B).]
What is usually the first sign of Sheehan’s syndrome, what causes it, and what is the treatment?
- First sign: Trouble lactating
- Cause: Pituitary ischemia following hemorrhage and hypotensive episode during childbirth
- Treatment: Hormone replacement
[Can also present with amenorrhea, adrenal insufficiency, and hypothyroidism.]
[UpToDate: Sheehan syndrome (ie, postpartum hypopituitarism) is a rare but potentially life-threatening complication. The pituitary gland is enlarged in pregnancy and prone to infarction from hypovolemic shock. Damage to the pituitary can be mild or severe, and can affect the secretion of one, several, or all of its hormones. A common presentation is a combination of failure to lactate postdelivery and amenorrhea or oligomenorrhea, but any of the manifestations of hypopituitarism (eg, hypotension, hyponatremia, hypothyroidism) can occur any time from the immediate postpartum period to years after delivery. If the patient remains hypotensive after control of hemorrhage and volume replacement, she should be evaluated and treated for adrenal insufficiency immediately; evaluation of other hormonal deficiencies can be deferred until four to six weeks postpartum.]
What effect does dopamine released from the hypothalamus have on the anterior pituitary?
Dopamine inhibits the release of prolactin from the anterior pituitary
Which 2 hormones does the posterior pituitary (neurohypophysis) secrete?
- Antidiuretic hormone (ADH)
- Oxytocin
[The posterior pituitary does not contain cell bodies.]
Most pituitary tumors respond to which drug?
Bromocriptine (dopamine agonist)
[Most common pituitary tumor is a prolactinoma.]
What is described as a benign calcified cyst (a remnant of Rathke’s pouch) that grows along the pituitary stalk to suprasellar location and can present with endocrine abnormalities, visual disturbances, headache, or hydrocephalus, and what is the treatment?
- Craniopharyngioma
- Treatment is cyst resection
[Diabetes insipidus is a frequent postoperative complication.]
[UpToDate: Craniopharyngiomas are epithelial tumors that usually arise in the pituitary stalk in the suprasellar region, adjacent to the optic chiasm. A small percentage arise within the sella, and a few tumors have been described within the optic system or the third ventricle.
Although benign histologically, these tumors frequently shorten life and should be considered low-grade malignancies. Most craniopharyngiomas contain both solid and cystic components. The cysts are filled with turbid fluid that contains cholesterol crystals.]
Which 5 hormones are released by the hypothalamus?
- Thyrotropin-releasing hormone (TRH)
- Corticotropin-releasing hormone (CRH)
- Gonadotropin-releasing hormone (GnRH)
- Growth hormone-releasing hormone (GHRH)
- Dopamine
What is Nelson’s syndrome?
Pituitary enlargement after bilateral adrenalectomy caused by increased corticotropin-releasing hormone (CRH)
[It can result in amenorrhea, visual problems (bi-temporal hemianopia), and hyperpigmentation from beta-melanocyte stimulating hormone (peptide byproduct of ACTH).]
[UpToDate: Patients who have had bilateral adrenalectomy for Cushing’s disease may develop corticotroph tumor progression (Nelson syndrome). Nelson syndrome was defined in an earlier era using sellar radiograms as the association of an enlarging pituitary tumor with progressive hyperpigmentation caused by very high plasma ACTH concentrations after bilateral adrenalectomy for Cushing’s syndrome. In addition to hyperpigmentation, other clinical manifestations due to the enlarging tumor were common, including headaches, visual field defects, and, sometimes, cranial nerve palsies. Most patients are now diagnosed at an earlier stage by magnetic resonance imaging (MRI) with smaller increases in tumor size (>2 mm). Therefore, symptoms related to the tumor itself are somewhat less common, but increased ACTH levels and hyperpigmentation are still important clinical manifestations.
Corticotroph tumor progression occurs in 8 %to 49% of adults and in over 50% of children with Cushing’s disease who undergo total surgical adrenalectomy without prior pituitary irradiation.
We suggest pituitary irradiation before adrenalectomy in patients with Cushing’s disease with radiologically detectable residual corticotroph tumor.
Once the tumor in a patient with Nelson syndrome becomes large enough to expand the sella, it is locally invasive, difficult to cure, and exhibits characteristics of a pituitary carcinoma. As a result, adrenalectomized patients should be followed indefinitely with MRI of the pituitary and measurements of basal and dexamethasone-suppressed plasma ACTH.
For patients who develop Nelson syndrome, we suggest early transsphenoidal surgery (before the tumor becomes a macroadenoma) (Grade 2C).
Progression of Nelson syndrome tumors may occur even after pituitary surgery. Therefore, for patients with persistent Cushing’s disease who have clear evidence of residual tumor after pituitary surgery, we suggest postoperative irradiation (Grade 2C). The type of radiation chosen is typically dictated by availability, cost, and patient preference regarding treatment time.
For patients without visible residual tumor, we do not recommend preventive radiotherapy but perform regular MRI and ACTH measurements.
In general, medical therapy is ineffective for the treatment of Nelson syndrome, with the exception of temozolomide, an alkylating agent, which was reported to be effective in cases of aggressive macroadenomas. Further data on temozolomide are required before this drug can be recommended in this setting.]
What visual defect is caused by a pituitary mass compressing the optic nerve (CN II) at the optic chiasm?
Bi-temporal hemianopia
What is the most common type of pituitary adenoma and what is the treatment?
- Most common pituitary adenoma: Prolactinoma
- Treatment: Bromocriptine or cabergoline (both are dopamine agonists), transsphenoidal resection for failure of medical management
[Most are microadenomas. Macroadenomas should be resected with hemorrhage, visual loss, CSF leak, or in patients who want to become pregnant. Bilateral pituitary tumors should be worked up by checking pituitary axis hormones and if normal the diagnosis is likely metastasis.]
Which 6 hormones does the anterior pituitary (adenohypophysis) secrete?
- Adrenocorticotropic hormone (ACTH)
- Thyroid-stimulating hormone (TSH)
- Growth hormone (GH)
- Luteinizing hormone (LH)
- Follicle-stimulating hormone (FSH)
- Prolactin
[The anterior pituitary does not have its own direct blood supply.]
