Pituitary Disorders

What is another name for Pituitary Adenomas?

pituitary neuroendocrine tumors

What classifies a microadenoma?

< 10mm/1cm

What classifies a macroadenoma?

>10mm/1cm

What are condition are pituitary adenomas associated with?

MEN-1

What type of pituitary adenomas are most prevalent?

Lactotroph adenomas

What is the most common type of pituitary adenomas?

Prolactinomas

What are common symptoms of macroadenomas?

HA, bitemporal hemianopsia, diplopia, hypopituitarism

What is the gold standard for diagnosis pituitary adenomas?

MRI of sell turcica with IV contrast

What is the first line treatment for symptomatic adenomas?

Transsphenoidal hypophysectomy

What is the first line treatment for asymptomatic adenomas?

observation and F/U

What is the first line treatment for prolactinomas?

Dopamine agonists (Cabergoline or bromocriptine)

What does prolactin stimulate?

lactation

What stimulates prolactin release?

increase estrogen, breastfeeding, nipple stimulation, meds, TSH

What is unique about prolactin?

It is under constant negative control by dopamine

What does prolactin suppress?

GnRH which in turn suppresses FSH/LH

What are common clinical manifestations of prolactinomas in women?

oligomenorrhea, amenorrhea, infertility, galactorrhea, low libido

What are common clinical manifestations of prolactinomas in men?

decreased libido, erectile dysfunction, hypogonadism, oligospermia/azoospermia, infertility, galactorrhea, gynecomastia

What are common clinical manifestations of prolactinomas in both men and women?

low bone density, fatigue, weight gain, insulin resistance, dyslipidemia

What are common mass effects of prolactinomas?

HA, visual field defects, blurred vision, cranial nerves palsies, hypopituitarism

What is biochemical testing should you conduct for prolactinomas?

serum prolactin, HCG, TSH

What value of serum prolactin is pathognomonic for macroprolactingomas?

> 500 ng/mL

What is the gold standard diagnostic test for prolactinomas?

pituitary MRI

What is second line treatment for prolactinomas?

transsphenoidal surgery

When/why would you perform surgery on a prolactinoma?

1) dopamine agonist resistance/intolerance/CI
2) pituitary apoplexy w/ mass effect
3) CSF leak
4) rapidly progressing visual field loss
5) nonadherence to meds

What is the difference between Gigantism and Acromegaly?

the timing of excessive production of GH in relation to the closer of the growth plate

What do you see in Gigantism that is not seen in Acromegaly?

major increases in height

What is the MCC of Giganistim/Acromegaly?

somatotroph GH-secreting adenoma of the anterior pituitary

What is causes of ectopic GH-production?

lymphoma, pancreatic islet cell tumors

What are common features of Gigantism/Acromegaly?

enlarged hands/feet, coarse facial features, HA, prominent forehead and brow, increased organ size, proximal muscle weakness, carpal tunnel syndrome

What is the initial screening test for Gigantism/Acromegaly?

measurement of IGF-1

What supports the presence of GH excess?

elevated IGF-1

If IGF-1 is elevated, what is the next test you should perform?

oral glucose suppression test

What result of the oral glucose suppression test would you suspect of someone with GH excess?

failure to suppress GH

What other hormones should you measure if you suspect someone has Gigantism/Acromegaly?

prolactin, T4, ACTH + cortisol, testosterone

What imaging should you do for someone suspected of Gigantism/Acromegaly?

pituitary MRI to R/O pituitary adenoma

If no pituitary source is found, what is the next imaging that should be done?

chest and abdominal imaging + measure GHRH

What is the first line treatment for someone with Gigantism/Acromegaly?

transsphenoidal surgery

What is a medical treatment for Gigantism/Acromegaly that may reduce tumor size?

somatostatin analogs (Octreotide)

What is a medical treatment for Gigantism/Acromegaly that blocks GH action on receptor?

Pegvisomant

What regulates the release of ADH?

1) increase in plasma osmolarity
2) decrease in blood volume
3) decrease in blood pressure

where are V1 receptors mainly located?

vascular smooth muscle

What is the main action of V1 receptors

vasoconstriction → increased blood pressure

Where are V2 receptors mainly located?

basolateral membrane of collecting duct principal cells

What is the main action of V2 receptors?

aquaporin-2 insertion into the apical membrane → increased water reabsorption

What does an increase in ADH cause?

increased water reabsorption → decreased urine volume → more concentrated urine

What was Arginine Vasopressin (AVP) Disorder previously called?

Diabetes Insipidus

What is AVP Disorder?

disorder of water balance caused by impaired vasopressin production, release, or action

What are characteristics of AVP Disorder?

excessive production of dilute urine, increase thirst and fluid intake, risk of dehydration and hypernatremia

What is AVP-D/CDI?

inadequate synthesis/release of AVP from the hypothalamus or posterior pituitary

What is AVP-R/NDI?

the V2 receptors, aquaporin-2 channels or the renal concentrating mechanism of the kidneys are not responding appropriately to AVP

What is the result of AVP Disorder?

decreased water reabsorption → dilute polyuria → increased plasma osmolarity → increased thirst

What is a hallmark finding of AVP Disorder?

> 3L/day of urine in adults with an osmolarity below 300 mOsm/kg

What is the first step for diagnosing AVP Disorder?

1) measure 24-hr urine volume
2) check urine osmolarity
3) measure serum sodium and plasma osmolarity

What are key findings of AVP Disorder?

high serum sodium + low urine osmolarity

Which test do you use to distinguish between AVP-D and AVP-R?

desmopressin response test (DDAVP)

What are the results of DDAVP that confirm AVP-D?

decreased UOP + significant increase in urine osmolarity

What are the results of DDAVP that confirm AVP-R?

no change in UOP and minimal/no change in urine osmolarity

What is the treatment for AVP-D?

desmopressin

What is the treatment for AVP-R?

correct underlying cause
if no underlying cause → NSAIDs or HCTZ

What is SIADH?

disorder of excessive or continued ADH activity

How do patients usually present clinically with SIADH?

with dilutional hyponatremia and clinically euvolemic

What does SIADH commonly present with?

water retention, low serum sodium, low serum osmolarity, inappropriatley concentrated urine

What is the management for SIADH patients with mild-to-moderate symptoms?

fluid restriction of <800 mL/day

What is the treatment for SIADH patients with severe symptoms?

urgent 3% hypertonic saline

What is the treatment for persistent SIADH?

IV Conivaptan or PO Tolvaptan