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ENDOCRINOLOGY > Pituitary/Hypothalamus > Flashcards

Pituitary/Hypothalamus Flashcards

1
Q

What is the embryologic origin of the neurohypophysis ?

A

Evagination of ventral hypothalamus and third ventricle

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2
Q

What is the embryologic origin of the adenohypophysis?

A

Rathke pouch (ectodermal evagination of the oropharynx)

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3
Q

What are the transcription factors involved in pituitary gland development?

A
  • SOX3, HESX1, LHX3, LHX4, PIT1, PIT 2: common to all
  • SF1: gonadotrops
  • GATA2: gonadotrops and thyrotropes
  • PROP1 and POU1F1: thyrotropes, lactotropes and somatotropes
  • TPIT, LIF, NEUROD1: POMC/corticotropes
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4
Q

What organs/glands secrete somatostatin?

A
  • Hypothalamus
  • Pancreatic islet cells
  • Gastrointestinal mucosa
  • C cells (parafollicular cells of thyroid)
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5
Q

What part of the hypothalamus is the satiety centre? Hunger centre?

A
  • Satiety centre = ventromedial hypothalamus
  • Hunger centre = lateral hypothalamus
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6
Q

_____-frequency pulses of GnRH favour FSH release while _____-frequency pulses favour LH release

A

Low-frequency pulses of GnRH favour FSH release while high-frequency pulses favour LH release

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7
Q

What are the populations of neurons involved in feeding/hunger that are located in the arcuate nucleus?

A
  • Neuropeptide POMC and CART (cocaine- and amphetamine-regulated transcript): inhibit food intake
  • Neuropeptide Y and ARP (agouti-related peptide): stimulate food intake
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8
Q

The pineal gland secretes _____

A

Melatonin

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9
Q

What drugs stimulate prolactin release? Inhibit?

A

STIMULATE: Dopamine antagonists (phenothiazines, haloperidol, risperidone, metoclopramide, reserpine, methyldopa, amoxapine, opioids)

INHIBIT: Dopamine agonists (levodopa, apomorphine, bromocriptine, pergolide), GABA

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10
Q

TSH _______ with age and BMI

A

Increases

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11
Q

List 3 contraindications to the insulin hypoglycemia test

A
  1. Elderly patients
  2. Patients with cardiovascular/cerebrovascular disease
  3. Patients with epilepsy
  4. ?Pediatric patients
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12
Q

What is the metyrapone test used for?

A
  • Assess adequacy of ACTH secretion
  • Blocks 11-beta hydroxylase (last step in cortisol synthesis), which decreases cortisol and increases 11-deoxycortisol. This should stimulate ACTH secretion.
  • Metyrapone may cause GI upset
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13
Q

What causes failure of GH suppression following a glucose load?

A
  • Acromegaly
  • Starvation
  • Protein-calorie malnutrition
  • Anorexia nervosa
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14
Q

How does obesity impact pituitary testing?

A
  • GH seceretion is impaired to all stimuli (insulin-induced hypoglycemia, arginine, levodopa, glucagon, GHRH)
  • Obesity causes hypogonadotropic hypogonadism in men
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15
Q

How does diabetes mellitus impact pituitary testing?

A
  • Most patients with DM1 have normal/elevated GH levels that do not rise further in response to hypoglycemia or arginine
  • IGF-1 levels are low despite elevated GH levels
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16
Q

How does uremia impact pituitary testing?

A
  • Basal levels of GH, PRL, LH, FSH, TSH and free cortisol are elevated (prolonged half life)
  • GH paradoxically increased following glucose administration
  • GH is hyperresponsive to hypoglycemia stimulus
  • Dexamethasone suppression of cortisol may be impaired
17
Q

How does starvation/anorexia nervosa impact pituitary testing?

A
  • GH secretion increases (may cause paradoxical increase in GH with glucose load)
  • Low levels of gonadal steroids
  • Cortisol levels increased, fail to suppress with dexamethasone
18
Q

How does depression impact pituitary testing?

A
  • Inability for dexamethasone to suppress plasma cortisol, elevated cortisol secretion
19
Q

______ % of the population harbour nonfunctional and asymtomatic pituitary adenomas

A

10-20%

20
Q

What is the sequence of aquired loss of pituitary hormones?

A
  1. GH
  2. FSH/LH
  3. TSH
  4. ACTH
  5. PRL

(Go Find The Adenoma Please)

21
Q

List a differential diagnosis for hypopituitarism

A
  • Invasive (ex. craniopharyngioma)
  • Infarction (ex. Sheehan syndrome)
  • Infiltrative (ex. Langerhans histiocytosis, sarcoidosis, hemochromatosis)
  • Injury (ex. severe head trauma)
  • Immunologic (ex. lymphocytic hypophysitis)
  • Iatrogenic (ex. surgery/radiation)
  • Infectious (ex. TB, syphilis, fungal)
  • Idiopathic (ex. familial, septo-optic-dysplasia)
  • Isolated pituitary hormone deficiency (various genetic causes)

(Nine I’s)

22
Q

What is pituitary apoplexy?

A
  • Spontaneous hemorrhagic infarction of a pituitary tumor (may also be related to diabetes mellitus, radiotherapy, or open heart surgery)
  • Acute pituitary failure results
23
Q

List 4 genetic conditions causing pituitary adenomas or hormone excess

A
  • MEN1 syndrome (MEN1) - prolactinomas
  • MEN4 syndrome (CDKN1B) - prolactinomas
  • Familial isolated pituitary adenomas (AIP) - GH secreting tumors
  • McCune-Albright syndrome (GNAS1) - GH hypersecretion
  • Carney complex (PRKAR1) - GH hypersecretion
  • X-linked acrogigantism (GPR101) - GH secreting tumors
  • Cushing’s disease (USP8) - ACTH
  • DICER1 (DICER1) - pituitary blastoma
  • Familial hyperprolactinemia (PRLR)
  • Pituitary adenomas (PTTG1) - all subtypes
  • Craniopharyngioma (CTNNB1 or BRAF genes)
24
Q

List 4 genetic conditions causing pituitary insufficiency

A
  • X-linked congenital adrenal hypoplasia (NROB1)
  • Early onset isolated ACTH deficiency (Tpit)
  • Kallman syndrome (KAL1, FGFR1, FGF8)
  • Combined pituitary hormone insufficiency (PROP1)
  • Congenital hypopituitarism (POU1F1/Pit1)
  • Other (LHX3, LHX4, PITX2, RPX)
25
Q

What are the 3 most common types of pituitary adenomas?

A
  1. 57% prolactinomas
  2. 28% nonfunctioning tumors
  3. 11% GH secreting tumors
  4. 2% corticotroph adenomas
  5. 2% unknown functional status

Hypersecretion of TSH, gonadotrophs and alpha subunits are very rare

26
Q

List a differential diagnosis for sellar/parasellar masses

A
  • BENIGN
    • Craniopharyngioma
    • Rathke cleft cyst
    • Meningioma
    • Enchondroma
    • Arachnoid cyst
    • Dermoid cyst
  • Empty sella
  • NONADENOMATOUS PITUITARY HYPERPLASIA
    • Lactotroph hyperplasia (pregnancy)
    • Somatotrophy hyperplasia (ectopic GHRH secreting tumor)
    • Thyrotroph, gonadotroph hyperplasia
  • Malignant tumors
  • Sarcoma
    • Chordoma
    • Germ cell tumor (ectopic pinealoma)
  • Metastatic lesions (breast, lung, other)
  • GLIOMAS
    • Optic glioma
    • Astrocytoma
    • Oligodendroglioma
    • Ependymoma
  • Vascular lesions
  • Granulomatous, inflammatory, infectious
    • Lymphocytic hypophysitis
    • Sarcoidosis
    • Histiocytosis X
    • Tuberculosis
    • Pituitary abscess
27
Q

Describe the triphasic response following pituitary surgery or CNS trauma

A
  1. Diabetes insipidus (early hypothalamic dysfunction)
  2. SIADH (release of ADH from the degenerating pituitary)
  3. Diabetes insipidus (depletion of AHD stores)
28
Q

LIst 3 clinical manifestations of hyperprolactinemia

A
  • Galactorrhea
  • Amenorrhea/hypogonadism/decreased libido
  • Headache, visual impairement, hypopituitarism
29
Q

What are the risks of pregnancy in women with prolactinomas?

A
  • Tumor expansion
  • Visual field defects
30
Q

List 10 manifestations of GH excess

A
  • Enlargement of hands and feet
  • Soft tissue overgrowth/coarsening of facial features
  • Increased sweating, heat intolerance
  • Oiliness of skin
  • Sleep apnea, Fatigue
  • Weight gain
  • Paresthesias
  • Joint pain
  • Photophobia
  • Papillomas
  • Hypertrichosis
  • Goiter
  • Acanthosis nigricans
  • Hypertension
  • Cardiomegaly
  • Renal calculi
31
Q

List 10 manifestations of Cushing disease

A
  • Obesity (with central fat distribution)
  • Moon (rounded) facies
  • Plethora
  • Hypertension
  • Glucose intolerance
  • Gonadal dysfunction
  • Osteopenia
  • Proximal muscle weakness
  • Easy bruisability, poor wound healing
  • Psychologic disturbance
  • Violaceous striae
  • Hirsutism, acne
32
Q

Surgery is first line treatment for Cushing disease. List 2 medical therapies that may be used as adjunctive therapy

A
  • Ketoconazole
  • Metyrapone
  • Less commonly used:
    • Mitotane
    • Etomidate
    • Cabergoline
33
Q

GHD occurs at CNS radiation doses above _____

A

18 Gy

ENDOCRINOLOGY (21 decks)

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