What is a pituitary adenoma?
Benign tumor of anterior pituitary cells
- May be functional or nonfunctional
How do nonfunctional pituitary adenomas present?
With mass effect:
- Bitemporal hemianopsia
What is the most common functional pituitary adenoma and how does it present?
- Galactorrhea and amenorrhea (females)
- Decreased libido and headache (males)
-->This is because prolactin promotes lactation of the breasts (females), but also inhibits GnRH synthesis and release, leading to decreased FSH and LH (males and females)
What is the treatment for a prolactinoma?
Dopamine agonists to inhibit prolactin secretion, leading to shrinking the tumor
What are the clinical features of Growth Hormone Adenomas?
- Gigantism in Children:
Linear growth of bones
- Acromegaly in adults:
Enlargement of the bones of the hands, feet and jaw
Growth of visceral organs (heart failure is most common cause of death)
- Secondary diabetes is often present
GH decreases glucose uptake into cells
How are Growth Hormone Adenomas diagnosed?
Elevated GH and IGF-1 (Insulin-like Growth factor) levels
Lack of GH suppression by oral glucose
How are GH adenomas treated?
- Octreotide: Somatostatin analog that blocks response of anterior pituitary to GHRH
- Growth hormone receptor antagonists
What are the types of functional pituitary adenomas
Prolactinoma (*Most Common)
Growth Hormone Adenoma
ACTH cell adenomas (secrete ACTH)
TSH cell, LH-producing, and FSH-producing adenomas are very rare
What is hypoptuitarism?
Insufficient production of hormones by anterior pituitary
--> symptoms don't often arise until >75% of pituitary parenchyma is lost
What are causes of hypopituitarism?
Pituitary adenoma (adults) (either by mass effect or bleeding into the adenoma - apoplexy)
Empty sella syndrome
What is Sheehan Syndrome?
During pregnancy there is a high demand for hormone and pituitary gland doubles in size, but blood supply doesn't increase as much and can lead to infarction during birth
- Patients present with:
loss of pubic hair (which suggests loss of androgens, which is actually a loss of LH and FSH from the pituitary)
What is empty sella syndrome? What causes it?
The sella tursica is empty and the pituitary is missing
Trauma to the pituitary and subsequent damage
Congenital defect of the sella with herniation of arachnoid and CSF into sella compressing pituitary and destroying it
What hormones are released from the posterior pituitary?
--> both made in hypothalamus and released by posterior pituitary
What is central diabetes insipidus?
- ADH deficiency
--> Due to hypothalamic or posterior pituitary pathology:
What are clinical features of Central Diabetes Insipidus?
Polyuria and Polydipsia
- Lack ADH, can't activate aquaporins
Hypernatremia and high serum osmolality
Low urine osmolality and specific gravity
How is diagnosis made for Central Diabetes Insipidus? Treatment?
- Water deprivation fails to increase urine osmolality
Treat with ADH: Desmopressin
What is Nephrogenic Diabetes Insipidus?
Impaired renal response to ADH
- Due to inherited mutations or drugs (i.e. lithium)
- Symptoms similar to central DI, but there is no response to desmopressin
What is SIADH? Symptoms?
Syndrome of Inappropriate ADH
- Excessive ADH secretion
Hyponatremia (cannot release water and end up diluting Na)
Low serum osmolality
Mental Status change and seizures (Hyponatremia leads to swelling of nerves and cerebral adema)
What are causes and treatments of SIADH?
Ectopic production (i.e. small cell carcinoma of the lung)
Drugs (i.e. cyclophosphamide)
Demeclocycline (blocks affect of ADH)