Pituitary Disorders Flashcards
1
Q
What is the best imaging modality for the pituitary?
A
MRI
- Posterior pituitary has bright spot on normal contrast
- with contrast, both anterior and posterior pituiary are bright
2
Q
Axes of the Pituitary
- how they differ?
- types of disorders
A
Anterior pituitary: hormones SYNTHESIZED and STORED
- Pituitary tumors
- Hypofunction
- Hyperfunction
Posterior Pituitary: Hormones are STORED only (hormones are synthesized by the hypothalamus)
- Diabetes insipidus
- SIADH
3
Q
Hormones produced by Anterior Pituitary
A
- FSH and LH: stimulated by pulsatile GnRH
- TSH: stimulated by TRH
- ACTH: stimulated by CRH
- PRL: stimulated by TRH; inhibited by dopamine
- GH: stimulates by GHRH
4
Q
Hormones produced by Posterior Pituitary
A
- AVP (Arginine Vasopressin)
- Oxytocin
5
Q
Hypopituitarism
A
- Diminished or absent secretion of >1 pituitary hormones
- Development often slow and insidious
- Clinical presentation depends upon etiology of hypopituitarism
6
Q
Hypopituitarism: Invasive causes
A
- Large pitutiary adenomas more likely to cause hypofunction than small pituitary adenomas (microadenomas)
- Look for compressive effect: e.g., Vision deficits due to compression of optic chiasm
7
Q
Sheehan’s Syndrome
A
- Hypopituitarism due to Infarction
- Mechanism for ischemia uncertain; believed to be hypotension and vasospasm of the hypophysial arteries, or due to shock
Clinical Symptoms: (75% of gland must be destroyed for symptoms to manifest)
- Failure to lactate
- Post-partum menstrual irregularities
8
Q
Lymphocytic hypophysitis
A
- IMMUNOLOGIC hypopituitarism that occurs during pregnancy and post-partum period
- Autoimmune process with infiltration of pituitary by lymphocytes and plasma cells that destroys anterior pituitary
- Pituitary autoantibodies may be present
- May result in isolated hormone deficiencies: ACTH deficiency most common
9
Q
Isolated anterior pituitary hormone deficiencies
A
- GH deficiency: usually presents in childhood
- Decreased muscle mass, increased fat mass; occult - Gonadotropin deficiency:
- Hypogonadotropic hypogonadism
- Kallman’s sydrome: defect in GnRH secretion and maldevelopment of olfactory center
- Amenorrhea, ED, decreased libido - TSH deficiency: incredibly rare; deficiency in TRH
- Fatigue, wt gain, cold intolerance - ACTH deficiency: incredibly rare; lymphocytic hypophysitis
- fatigue, weakness - PRL deficiency: sign of severe hypopituitarism
- Lactation failure
10
Q
What hormone provides NEGATIVE INHIBITORY CONTROL over Prolactin?
A
Dopamine
- During damage to anterior pituitary, Prolactin levels are the most resistant to change
11
Q
Primary (ADDISON’S) vs. Secondary Adrenal Insufficiency
A
Note: aldosterone made by adrenal gland is more under the control of renin angiotensin (secreted by kidney) than ACTH (pituitary)
- Primary Adrenal Insufficiency (ADDISON’S DISEASE): will have low aldosterone, but high ACTH
- Secondary: when you have pituitary deficiency with low ACTH production , you are going to get all the manifestation of cortisol decrease but not aldosterone decrease.
- present with hyponatremia but not hypokalemia
- tend not to see hypotension as with aldosterone deficiency
12
Q
Stimulation Testing
- ACTH Stimulation Test
A
- Useful for diagnosis of adrenal insufficiency and growth hormone deficiency
- After measuring baseline ACTH & Cortisol/Alodsterone, administer COSYNTROPIN (analog of ACTH)
- High baseline ACTH: admin of cosyntropin does not raise cortisol/aldosterone –> Primary Adrenal Insufficiency
- Low baseline ACTH: admin of cosyntropin does not raise cortisol/aldosterone –> Central (Secondary) adrenal insufficiency
13
Q
Treatment for Adrenal Deficiency
A
- Administer Glucocorticoids (e.g., hydrocortizone or prednisolone
14
Q
Treatment for TSH Deficiency
A
- administer Levothryoxine
** If adrenal insufficiency is suspected with hypothyroidism, treat with glucocorticoids (steroids) prior to levothyroxine
15
Q
Pituitary Adenomas (Clinical presentation)
A
Early manifestations: Signs of hypogonadism and oligomenorrhea/amenorrhea
Late manifestations:
- Mass effect: headache, peripheral visual deficit
- Specific symptoms of hormone hypersecretion
- Lactotrophs (60%)
- Somatotrophs (20%) - acromegaly
- Corticotrophs (10%) – Cushing disease
- Thyrotrophs
- Gonadotrophs
- Pituitary insufficiency once tumor becomes big enough
16
Q
Bitemporal Hemianopsia
A
- Bilateral peripheral visual deficit
- due to compression of optic chiasm
- often compressed by mass effect of pituitary adenomas
17
Q
Prolactinoma
A
- Prolactin-secreting tumors
- Microprolactinoma 10 mm in size; More common in men (present late)
- PRL level correlates with size of prolactinoma
Presentation: Prolactin increases milk production, decreases GnRH
- menstrual irregularities
- Galactorrhea (perform a thorough physical exam)
- visual field defects (33% with macroadenomas)
- Headache
- libido-potency failure (dereased gonadal function)
Treatment:
- DOPAMINE inhibits prolactin secretion
- Limiting factor for radiotherapy: need at least 5mm space from pituiary to optic chiasm
18
Q
Dopamine Agonists
A
- Bromocriptine : D1 and D2 receptors
- Cabergoline : more specific for D2 receptor
- long half life & long duration of action
- Contraindications: uncontrolled HTN or known sensitivity to ergot derivatives
- Metabolized in the liver
- Advise to take at bedtime: nausea, headache, dizziness, mental fogginess
19
Q
Treatment of Primary Hypothyroidism with elevated prolactin secretion
A
- Treat primary hypothyroidism first
- hypothyroidism will cause increase in TRH and TSH
- TRH will override inhibitory effect of dopamine, and stimulate excess secretion of prolactin
- Prolactin levels should normalize after treatment of primary hypothyroidism with levothyroxine
20
Q
Acromegaly
A
- Due to excess GH secretion, typically caused by pituitary adenoma
Findings: large tongue, hands & feet; enlarged angled jaw; deep voice; impaired glucose tolerance (insulin resistance)
- No linear growth because fused long bone epiphyses
Diagnosis:
- increased serum IGF-1; GH stimulates HEPATIC secretion of IGF-1
- Glucose suppression test: oral glucose load (75g) and measure GH at baseline, 1h and 2h
- Normal: GH very low
- GH excess: GH does not suppress
- Imaging after biochemical confirmation to determine etiology of GH excess (majority of cases pituitary adenoma > 1 cm)
Tx: Surgery is first line
21
Q
Gigantism
A
- excess GH secretion in children
- increased linear bone growth
- Concomitant hypogonadism also delays epiphyseal closure
22
Q
What suppresses GH release?
A
- Glucose
- Somatostatin: GH inhibitory hormone
- Pegvisomant: GH receptor antagonist
23
Q
Cushing’s Disease
A
- Pituitary adenoma secreting excess ACTH
- Insidious onset of symptoms of cortisol excess:
Presentation:
- Obesity, central fat distribution, moon facies
- HTN
- glucose intolerance
- gonadal dysfunction
- proximal muscle weakness
- easy bruising, striae
- hirsutism, acne
Diagnosis: 24 HOUR URINE FREE CORTISOL
Treatment: transsphenoidal surgery +/- medical therapy
24
Q
Gonadotropin-secreting adenoma
A
- Usually secrete FSH>LH
Clinical presentation: hypogonadism and hypopituitarism due to large size at time of diagnosis
No medical therapy available: primary treatment is surgical
**Note that if patient presents with elevated FSH and LH, diagnosis likely primary gonadal failure (or menopause)
25
TSH-oma
- Incredibly rare!
- Presentation: Hyperthyroidism with goiter without exopthalmopathy (Graves’)
- Lab: Elevated TSH and thyroid hormones
MRI: Pituitary adenomas usually large
Treatment: surgical; Somatostatin analogs can be helpful
26
Multiple Endocrine Neoplasia Type 1
3 P's:
1. Pituitary adenomas (prolactinoma, growth hormone)
2. Parathyroid adenomas (or hyperplasia)
3. Pancreatic tumors (gastrinoma, insulinoma)
Presentation: commonly with kidney stones and stomach ulcers
Autosomal dominant inheritance of MEN1 gene from chromosome 11
27
MEN 2A
2P's
1. Parathyroids
2. Pheochromocytomas
3. Medullary thyroid carcinomas: secrete calcitonin
28
MEN 2B
1P:
1. Pheochromocytoma
2. Medullary thyroid carcinoma
3. Oral/intestinal ganglioneuromatosis
29
Pituitary Apoplexy
- Caused by HEMORRHAGIC NECROSIS of a tumor or pituitary gland infarction
- Can be presenting sign of a pituitary adenoma
- An endocrine EMERGENCY
Clinical presentation:
- Sudden-onset headache (mostly frontal)
- Visual (acuity, field) loss
- Ophthalmoplegia
- Meningismus
- Altered mental status
- Vomiting
- Fever
- Nausea, vomiting
- Hypotension
30
Empty Sella Syndrome
- Sella turcica partially filled with CSF, causing Sella to enlarge and pituitary to flatten
- Partial empty sella: congenital incompetence of diaphragm sellae surrounding normal pituitary
- occurs after pituitary surgery or radiation therapy
- Usually middle-aged obese women
- Associated with systemic HTN or benign intracranial hypertension
- Pituitary function almost always normal
31
Function of AVP
- with low BP, induces AQP channel formation at collecting duct to allow reabsorption of water into the vasculature
- without AVP, water is lost in the urine
32
Central diabetes insipidus
- Def: Deficiency of AVP
Spontaneous DI
- Infiltrative diseases (sarcoidosis, histiocytosis)
- Lymphocytic hypophysitis (or lymphocytic infundibuloneurohypophysitis)
- Head trauma
- Neurosurgery
* *Sellar lesions and pituitary adenomas are NOT common causes of DI
* * If sellar lesion present with DI, suggests metastatic disease (vs. primary anterior pituitary adenoma)
Clinical presentation: always thirsty; frequent urination
Lab: Hypernatremia and serum hyperosmolality, with inappropriately dilute urine (low urine osmolality)
Dx: Water deprivation test: can they concentrate their urine?
33
SIADH
- Syndrome of Inappropriate ADH secretion
- Elevated urine sodium excretion while on normal salt and water intake
- Hypoosmolality of ECF and plasma
Clinical: will be euvolemic
- no orthostasis, tachycardia, decreased skin turgor, dry mucous membranes to suggest hypovolemia
- no edema, ascites to suggest hypervolemia
Common causes:
- Tumors
- CNS disorders
- Drug-induced
- Pulmonary diseases
- Prolonged exercise (marathon running)
Management:
- Treat the underlying disorder
- Fluid restriction
- IV hydration likely to worsen hyponatremia as patient will retain more free water
34
Panhypopituitarism
- Typically, GH production falls 1st, followed
by FSH/LH, TSH, and ACTH last
- Order not followed in all cases
- ADH deficiency rare with pituitary disease,
more common after surgery on pituitary
- PRL will be least affected b/c under inhibitory control of dopamine
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Causes:
Pituitary non-functional tumor
Compression of stalk
Post-partum shock (Sheehan’s syndrome)
Inflammation (autoimmune lymphocytic
hypophysitis)
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35
Craniopharyngiomas
- Tumor that arises from epithelial remants of Rathke's pouch in the sella turscia
- presents as a supratentorial mass in children
- may compress the optic chasm
- calcifications are common
- may have keratin-filled cysts
