Anterior Pituitary

Question 1

How does PRL modulate GnRH?

Answer 1

Modulates LH and FSH secretion

- PRL inhibits GnRH secretion

Question 2

What are some physiologic responses that lead to PRL release/inhibition?

Answer 2

Activation:
TSH
Pregnancy
Nipple sucking
Lactation 
Estrogen
Stress

Inhibition:
Dopamine via stalk (ie. stalk effect)

Question 3

What is the name of PRL excess?

Answer 3

hyperprolactinemia

Question 4

What are the pre-clinical features of hyperlactinemia in pre-menopausal?

Answer 4

Most have small tumors (microadenoma)
Disruption of regular menstrual periods
Irregular, longer cycle length, amenorrhea (lack of periods)
Infertility
Galactorrhea (milky breast discharge) in 30-80%

Question 5

What are the pre-clinical features of hyperlactinemia in post-menopausal?

Answer 5

No longer have menstrual disturbance as clinical clue
Can still have galactorrhea
Symptoms of large tumors: Headache, Visual Field abnormalities, hypopituitarism

Question 6

What are the pre-clinical features of hyperlactinemia in men?

Answer 6

Usually large tumors (macroadenomas)
Symptoms of hypogonadism: Reduced sex drive, erectile dysfunction
Symptoms of large tumors: Headache, Visual Field abnormalities, hypopituitarism

Question 7

What is the treatment for prolactinoma?

Answer 7

Dopamine agonist therapy:

• Cabergoline (most common, most effective, long T1/2)
• Bromocriptine (oldest, daily)
• Quinagolide (least common, role where others are not well tolerated)

In microadenomas, can often be withdrawn after a few years, or after menopause.

In macroadenomas, therapy is typically required lifelong
Surgery rarely performed because of low success rate, in particular macroadenomas.

Question 8

What are the clinical features of acromegaly?

Answer 8

Physical:
Soft tissue swelling
Spade-like hand, increased ring size, shoe size, macroglossia (large tongue)
Bony overgrowth
Frontal bossing (prominent forehead), prognathism (protruding jaw), coarse facial features
Can lead to dental malocclusion
Cartilage overgrowth
Osteoarthritis, reduced mobility
All of above can lead to Nerve entrapment, notably carpal tunnel syndrome
Excessive sweating

Biochemical/Symptoms:
Insulin resistance
Impaired glucose tolerance, diabetes
Increased skin tags
Hypertension
Headaches
Mass effects: Hypogonadism-Fatigue, sexual dysfunction; visual disturbance
Sleep apnea
Multinodular goiter

Question 9

How to investigate if GH is in excess?

Answer 9

1. Plasma IGF-I= Screening test
2. If IGF-1 is elevated, proceed with a suppression test
   –> induce hyperglycemia
   –> 75 g Oral Glucose tolerance test
   Give glucose load and measure blood glucose and GH levels simultaneously every 30 minutes for at least 2 hrs
   Normal: GH suppressed to < 0.4 mcg/L after glucose administration
   Acromegaly: GH commonly not suppressed by glucose, may show paradoxical rise

Question 10

What are the treatments for GH secreting tumour?

Answer 10

1st line treatment= Surgery (transsphenoidal or transfrontal)

Somatostatin analogues (octreotide, lanreotide, pasireotide)
- Act like Somatostatin on pituitary and inhibit production of GH and in turn IGF-1