Disorders of the Anterior Pituitary Flashcards Preview

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Flashcards in Disorders of the Anterior Pituitary Deck (22):
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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 

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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

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Two common stimuli for GH secretion?

hypoglycemia and starvation. GH anatgonizes insulin

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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

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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

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Why would loss of vision be assoicated with a pituitary tumor?

The optic chiasm lies just above the pituitary (bitemporal hemianopsia)

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Clinical features of acromegaly?

acral enlargement

frontal bossing and coarsening of fewatures with aging 

excessive sweating

arthralgias

Headache

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Acromegaly carriers a slight increase in which cancers?

Colorectal polyps, and esophagus, stomach, and melanoma cancers

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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

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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

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What is the most appropriate next diagnostic test?

Serum insulin like growth factor-1 measurement

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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

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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

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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!

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Tx of prolactinoma?

Dopamine agonists can shrink tumors, address visual problems, and restore gonadal function

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TSH-secreting tumors. Tx?

Rare tumors of the pituitary causing overproduction of TSH that presents in labs with BOTH elevated T4/T3 and TSH and confirmed via MRI. Tx is neurosurgical resection

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Gonadotropin female axis

Gonadotropin male axis

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AE of haloperidol?

dopamine antagonist so it may cause elevated prolactin levels 

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In additio to assessing adrenal and thyroid function, what else should be done?

Serum prolactin measurement

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Tx?

Dopamine agonist first!! 

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