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Diabetes and Endocrinology YR3 > Pituitary Gland lecture > Flashcards

Pituitary Gland lecture Flashcards

1
Q

Location and relations

A

Base skull
Sella tursica
Attached to hyppthalamus via stalk
Cavernous sinuses either side
Optic chiasm superiorly

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2
Q

Size of pituitary

A

13mm x 9mm 100mg

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3
Q

When does pituitary size change?

A
  • Doubles pregnancy
  • Shrinks elderly
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4
Q

Blood supply to pituitary

A
  • Hypothalamo-hypophyseal portal system
  • Derived from superior and inferior hypophyseal arteries
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5
Q

Venous drainage of pituitary

A
  • Through cavernous sinus into petrosal sinuses and internal jugular veins

Important to know this for venous sampling

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6
Q

What is produced by pituitary gland?

A

8 hormones
6 anterior - FSH, LH, GH, ACTH, TSH, Prolactin
2 posterior - ADH and oxytocin - just stores these, does not produce

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7
Q

What is hypopituitarism

A

Partial or complete deficiency of anterior and or posterior pituitary hormones
May be all hormones, partial or singular
Can be primary or secondary due to hypothalamus pathology

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8
Q

Causes of hypopituitarism

A
  • Pituitary or parapituitary tumours eg meningioma, mets
  • Radiotherapy
  • Infarction - apoplexy, Sheehans
  • Infiltration - sarcoidosis, lymphocytic, haemachromotosis
  • Infection - eg TB/abscess
  • Trauma or SAH
  • Isolated deficiencies - Kallmanns
  • Genetic
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9
Q

Clinical manifestations of hypopituitarism

A
  • GH - short stature if occurs when under 18, reduced exercise capacity
  • FSH/LH - amenorrhoea, anovulation, erectile dysfunction, reduced libido
  • ACTH - hyperkalaemia, hypoadrenal crisis
  • TSH - hypothyroidism
  • PRL - failure lactation
  • ADH - polyuria and polydipsia
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10
Q

Investigations for hypopituitarism

A
  • Basal hormone levels (cortisol done at 9am when highest)
  • Investigate cause - MRI, serum ACE (sarcoid), hCG, ferritin (haemochromatosis) AFP (tumours)
  • Biopsy?
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11
Q

Dynamic testing for growth hormone

A
  • Glucagon
  • Arginine
  • Insulin tolerance test

All try to stimulate glucagon production

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12
Q

Dynamic testing for ACTH

A
  • Short synacthen test
  • Also long - not really used now
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13
Q

Dynamic testing for FSH and LH

A

GnRH administration

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14
Q

Test for ADH deficiency

A
  • Plasma and urine osmolarity
  • Urine Na
  • Fluid deprivation test - see if urine concentrates
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15
Q

Signs of hypersecretion of pituitary hormones

A

Acromegaly
Cushings

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16
Q

Most common brain tumour

A

Adenoma

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17
Q

Classification of pituitary tumours

A
  • Size - macro vs micro
  • Functional vs non-functional
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18
Q

Order of incidence of adenoma types

A
  1. Prolactinoma
  2. Non functioning - mass effect
  3. GH - acromegaly
  4. ACTH adenoma -Cushings disease
  5. TSH adenoma - RARE
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19
Q

Physiological causes of hyperprolactinaemia

A
  • Pregnancy
  • Breastfeeding
  • Exercise
  • Stress
  • Sleep
  • Seizure
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20
Q

Pharmacologcal causes of hyperprolactinaemia

A
  • Dopamine antagonist - eg haloperidol, risperidone, metoclopramide
  • MAO inhibitors - parkinsons
  • Cimetidine
  • Verapamil
  • Thyrotropin releasing hormone test
21
Q

Pathological causes of hyperprolactinaemia

A
  • Pituitary tumours (prolactinoma)
  • Hypothyroidism
  • CKD
  • PCOS
22
Q

Presentation of prolactinoma

A
  • Galactorrhoea
  • Amenorrhoea/irregular periods
  • Reduced libido
  • Erectile dysfunction

or mass effect:
* Headache
* CN involvement
* CSF leak
* Hypopituitarism - if compresses

23
Q

Investigations for prolactinoma

A
  • MRI
  • PRL level (less than 2000 suggests micro/stalk effect, more than 4000 means macro)
  • Pituitary function tests
24
Q

What is the hook effect?

A

Antibodies are bound to some prolactin so some is not read in blood test
If they dilute sample and re do - can trust sample

25
Q

What is macroprolactin?

Larg

A

Large aggregates - prolactin appears larger value than it actually is
Use polyethylene glycol to rule out (PEG

26
Q

What is stalk effect?

A

High levels of prolactin occur due to compression of pituitary stalk causing reduced dopamine release
= decreased inhibition of prolactin not actually prolactinoma

27
Q

Aims of treatment for prolactinoma

A

Micro - restore gonadal function
Macro - reduce size and restore function

28
Q

Options of treatment for prolactinoma

A
  • Dopamine agonists eg Cabergoline, Bromocriptine, Pergolide, Oestrogen
  • Surgery sometimes if compressing chiasm, aggressive
  • Radiotherapy sometimes too
29
Q

Presentation of acromegaly

A
  • Sweating
  • Headache
  • Tiredness
  • Joint pain
  • Change in shoe/ring size - enlarged hands and fingers
  • Frontal bossing - prominent forehead
  • Enlarged nose
  • Prognathism - bulging jaw
  • Macroglossia
  • Carpal tunnel
  • Organomegaly
30
Q

Associated co-morbidies with acromegaly

A
  • HTN
  • DM
  • OSA
  • IHD
  • CHF
  • Colonic polyps
31
Q

Acromegaly tests

A
  • IGF1 and random GH - not very helpful
  • OGTT - should supress GH to less than 0.33
  • MRI
  • Pituitary function test
  • GNRH - ectopic secretion from carcinoid tumour if no pituitary lesion
32
Q

Treatment for acromegaly cuased by pituitary tumour

A
  • Transphenoidal surgery
  • Radiotherapy
  • Medical - somatostatin anologies, dopamine agonists, GH receptor antagonist
33
Q

Causes Cushings syndrome

A
  • Pseudocushings - alcoholism, severe depression
  • Adrenal adenoma/carcinoma/nodular hyperplasia
  • Exogenous steroids
  • Ectopic ACTH or CRH
34
Q

Cause of cushings disease

A

Pituitary adenoma secreting ACTH

35
Q

Associated features of Cushings

A
  • HTN
  • DM
  • Osteoporosis
  • Recurrent infections
36
Q

Investigations for Cushings

A
  • 2x 24hr urine cortisol test
  • Overnight dexamethasone supression test
  • Salivary cortisol
  • Midnight cortisol
  • Low dose dexamethasone supression test - 100% sensitive almost and then high dose
  • ACTH
  • K+
  • CRH
37
Q

Ectopic ACTH vs pituitary ACTH test results

A

Low K - mostly in ectopic
Supression on HDDST - supressed in pituitary (not ectopic)
Rise when CRH given - pituitary

38
Q

If unsure if pitutary cushings, another invasive test can do?

A

Inferior petrosal sampling
Compare ACTH to serum
If peripheral ratio is more than 2x suggests pituitary cushings
Ratio of more than 3 after CRH given is diagnostic

39
Q

Treatment of cushings disease

A
  • Transphenoidal surgery
  • Radiotherapy
  • Adrenalectomy (can cause Nelsons syndrome)
  • Medical - Ketoconazole, Metyrapone
40
Q

What is Nelsons syndrome?

A

ACTH production increases when cortisol decreases if remove adrenals
= enlarge tumour

41
Q

What is diabetes insipidus defined as?

A

Passage of more than 3L per day of dilute urine
Osmolality less than 300mosm/kg

42
Q

Clinical symptoms of DI

A
  • Polyuria
  • Polydipsia
  • Nocturia
43
Q

2 types DI

A
  • Cranial or nephrogenic
44
Q

Cause of cranial DI

A
  • Congenitial (DIDMOAD - diabetes insipidus, DM, optic atrophy, deafness)
  • Acquired due to trauma, infection, infiltration, inflammation, vascular
45
Q

Nephrogenic diabetes cause

A
  • Familial
  • Acquired - drugs, metabolic, CKD, post obstructive uropathy
46
Q

DI investigations

A
  • More than 3L per day urine
  • Exclude DM, hypercalcaemia, renal failure
  • Water deprivation test - if less than 300mosm/kg then diagnostic
  • Then do desmopressin admistration to see if osmolarity changes by more than 50% - if it does = cranial
  • MRI brain
47
Q

Treatment of DI

A

Cranial - desmopressin
Nephrogenic - Indomethacin, Thiazide, high dose desmopressin

48
Q

How does Indomethacin work?

A

NSAID - blocks action of prostaglandins at kidney
= less inhibition of ADH

49
Q
A

Diabetes and Endocrinology YR3 (28 decks)

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