Disorders of the Anterior Pituitary Flashcards
What is Sheehan syndrome?
During pregnancy the pituitary becomes large and vascular so if the mother bleeds a lot post-partum it can become necrotic and hypo-piutitiarism occurs
Why cant GH levels be used to diagnose acromegaly?
Because GH levels are so transient throughout the day and are secreted in a pulsatile fashion
Two common stimuli for GH secretion?
hypoglycemia and starvation. GH anatgonizes insulin
How does acromegaly present?
insidious onset with very slow progression and an average interval from onset of symptoms until diagnosis of 12 yrs. At diagnosis, about 75% have macroadenomas (tumor diameter 10+mm) and some of the adenomas extend to the parasellar or suprasellar regions
Clinical presentation of acromegaly? Most common cause of death?
The clinical features are attributable to high serum GH and IGF-1 (a byproduct of GH produced at target tissues)- both have effects of nitrogen retention, insluin antagonism, and lipolysis and include: large tongue, deep voice, large hands and feet, diaphoresis, and frontal bossing
The mortality rate of patients with acromegaly is increased with death occurring most commonly due to CV disease
Why would loss of vision be assoicated with a pituitary tumor?
The optic chiasm lies just above the pituitary (bitemporal hemianopsia)
Clinical features of acromegaly?
acral enlargement
frontal bossing and coarsening of fewatures with aging
excessive sweating
arthralgias
Headache
Acromegaly carriers a slight increase in which cancers?
Colorectal polyps, and esophagus, stomach, and melanoma cancers
How would acromegaly be diagnosed?
Do not measure GH, instead measure IGF-1 levels and follow with a OFTT (oral glucose tolerance test)
In normal subjects GH levels should suppress to 1 ng/ml 2 hr after ingestion of 75g of glucose. In acromegaly, GH levels are elevated above 2 ng/ml after an OGTT
How is acromegaly treated?
For microadenomas, macroadenomas that appear to be fully resectable, and macroadenomas causing vision impariment, transsphenoidal surgery is the treatment of choice
Macroadenomas abutting or adjacent to the chiasm should be decompressed surgically
For others, Tx includes a long acting somatostatin analogue (octreotide) or pegvisomant
What is the most appropriate next diagnostic test?
Serum insulin like growth factor-1 measurement
Describe the epidemiology of prolactinomas
Aka lactotroph adenomas, these are common in women in their 30s and account for approx. 40% of all pituitary tumors and produce prolactin levels 250+ ug/l, especially if a macroprolactinoma (10+mm in diameter). Note: The most common cause of hyperprolactinemia is a prolactinoma and the occurence of these tends to increase durign pregnancy and can lead to visual problems
Normal prolactin: 25ug/l
How do prolactinomas present?
Can be asymptomatic or produce various syndromes such as hypogonadism, menstrual abnormalities, infertility, galactorrhea, and bone loss secondayr to sex steroid hormone attenuation
How is Prolactinoma diagnosed?
A single measuremnt of serum prolactin above the upper limit confirms the diagnosis (normal less than 25ug/l). Prolactin 250+ug/l usually is diagnostic and greater than 500ug/l is diagnostic for macroprolactinoma BUT
dopamine antagonists can elevate prolactin levels!
Gonadotropin female axis
Gonadotropin male axis
In additio to assessing adrenal and thyroid function, what else should be done?
Serum prolactin measurement
Tx?
Dopamine agonist first!!
