Pituitary Adenomas

Question 1

4 Ways They Present

Answer 1

• Mass effect - macroadenomas esp
• Hypopituitarism (can be adenoma or multiple other causes)
• Hormone excess - Prolactin, GH, ACTH, TSH (hyper-secretion is almost always adenoma)
• Incidental finding on imaging

Question 2

Categorization of Pituitary Adenomas

Answer 2

• 70% hyper-secretion, 25% null-cell adenoma (no apparent hormone), 2% plurihormonal
• By Specific Hormone
  
  • Prolactin secreting most common
  • Then null cell adenoma or gonadotropin (FSH, LH, alpha subunit)
  • GH/ACTH 10% ea
  • Rare - TSH or plurihormonal
• By size
  
  • Micro < 1 cm - less likely to cause hypopituitarism; rarely progress
  • Macro > 1 cm - 50% have mass hypopituitary effect; more aggressive

Question 3

Possible Consequences of Macroadenoma

Answer 3

• Can cause CN palsies or rare temporal seizures if lateral extension into cavernous sinuses or temporal lobe
• If stretch dura above - headaches
• Bitemporal field defects if affect optic chiasm
• CSF rhinorrhea if downward

Question 4

GH Hypersecretion Presentation

Answer 4

• Soft tissue growth - coarsening of facial features and enlargement of hands/feet (inc ring size, shoe size, hat size), arthralgias (OA from cartilage growth), median nerve compressed w/ soft tissue swelling, stimulates sweat glands, diabetogenic, sodium retention, organs enlarged (including thyroid - goiter- higher rate thyroid cancer), sleep apnea (enlarged tongue), cardiomyopathy from enlarged heart, inc lipids in blood inc CV risk, widely spaced teeth, colon polyps
• Often insidious / dx missed for many yrs
• Often macroadenoma - check for visual defects; may have headaches
• 20% co-secrete prolactin (sometimes secrete TSH)

Question 5

GH Tumor Tx

Answer 5

• surgery (transphenoidal adenomectomy) then recheck IGF-1 3 mo after
• If persistent - use meds
• Octreotide - somatostain analog (GH secretion inhibitor); monthly IM injection (GI upset, impaired glucose tolerance, cholethiasis)
• Lantreotide - monthly subQ injection
• Pegvisomant - GH analog that prevents receptor dimerization to dec IGF-1 synthesis; no tumor shrinkage but less GI effects and better diabetic control
• Cabergoline - dopamine agonist; best for patients w/ prolactin co-secretion; cheaper and oral; can be added to others
• If still persists - gamma knife radiosurgery (as long as >3-5 mm from optic chiasm)

Question 6

Prolactinoma Presentation

Answer 6

inappropriate lactation, oligomenorrhea or amenorrhea in women, hypogonadism in men, delayed puberty

-B/c prolactin dec GnRH - dec sex hormones

Question 7

Prolactinemia Dx Based on Amount

Answer 7

• > 200 almost always prolactinoma
• 100-200 probably prolactinoma (could also be compression of stalk)
• < 100 could be primary hypothyroid or pregnancy or using neuroleptics or micro prolactinoma

Question 8

Prolactinoma Tx

Answer 8

• only one treated w/ meds first then surgery
• Dopamine agonist - bromocriptine (shorter half life for preg), cabergoline (preferred more potent/effective and only twice weekly dose)
• Dec PRL DNA synthesis so tumor shrinkage (often visual and reproductive problems resolve)
• Drugs bind D2 receptor - G alpha inhibitory subunit –> dec adenylyl cyclase –> dec cAMP –> dec prolactin gene transcription

Question 9

ACTH Excess

Answer 9

• Causes 75% of all Cushing Syndrome from extra cortisol (another lecture)
• Usually ACTH secreting adenomas are small (40% not seen on MRI)
• 30s - 50s; women > men
• High mortality from CVD and inc risk infections
• Tx - surgery is first-line, also gamma knife, meds

Question 10

TSH Excess

Answer 10

• RARE (<1%)
• Present w/ classic hyperthyroid symptoms but no extrathyroid manifestations as seen in Graves’; no TSH suppression (this is tip-off)
• Commonly co-secretion of alpha subunit or GH / hyperprolactinemia
• Tend to be large and aggressive
• Often delay tx b/c misdiagnose as thyroid problem
• Tx - surgery and irradiation; may use octreotide to normalize thyroxine and cause tumor shrinkage if needed (octreotide dec TSH production)

Question 11

2 Types of Clinically Non-Functioning Pituitary Adenomas

Answer 11

1- FSH/LH Hyper-secretion

- Usually elevated FSH/LH means gonadal failure BUT may be due to pituitary tumor
- Usually discovered due to mass effect from growth - headaches, visual disturbance

2- Null Cell Adenoma
- 10% spont regress so “wait and see” approach if no visual field defect (do annual MRI for monitoring)

FOR BOTH - no meds; perform surgery only if symptomatic