Lectures Flashcards
What is the anterior pituitary lobe like?
Anterior lobe: glandular tissue, accounts for 75% of total weight.
What is the posterior pituitary lobe like?
Posterior: nerve tissue & contains axons that originate in the hypothalamus.
What is the development of the pituitary gland like?
anterior and posterior pituitary have different points of origin
Label this image
Label
Label the pituitary and surrounding anatomy (coronal)
Label this coronal section
Does the anterior pituitary have blood supply?
The anterior pituitary has no arterial blood supply but receives blood through a portal venous circulation from the hypothalamus
What is the control of vasopressin release and its action?
What is oxytocin action?
Actions of the anterior pituitary?
What are the different negative feedback loops of the pituitary gland?
slide 15
What does the pituitary effect?
growth
thyroid
puberty
steroids
What is the action and effects of the growth hormone?
HPA axis
What is the structure of the thyroid gland?
What is the synthesis of T4 and T3?
What is the thyroid hormone function?
- Accelerates food metabolism
- Increases protein synthesis
- Stimulation of carbohydrate metabolism
- Enhances fat metabolism
- Increase in ventilation rate
- Increase in cardiac output and heart rate
- Brain development during foetal life and postnatal development
- Growth rate accelerated
?
In periphery T4 converted to T3
Half life T4 – 5 to 7 days
Half life T3 – 1 day
Cortisol action
What does ACTH stimulate?
ACTH stimulates cortisol and androgen release from Adrenal gland
What does ACTH by pituitary regulate?
HPG axis
What is Steroidgenesis in the gonads?
hyperprolactinaemia?
prolactin secretion
How do pituitary diseases present?
What does a large pituitary tumour cause?
Tumours cause:
1. Pressure on local structure e.g. optic nerves
- Bitemporal hemianopia
2. Pressure on normal pituitary
- hypopituitarism
3. Functioning tumour
- Prolactinoma
- Acromegaly
- Cushing’s disease
What can pressure on local structures cause?
How do you measure visual field defects?
What can pressure on pituitary cause?
Hypopituitary man
- Pale
- No body hair
- Central obesity
What are the causes of hypopituitarism?
Pituitary tumours
Radiotherapy
Trauma
Infarction
Infiltration e.g. sarcoidosis, haemochromatosis
Infection e.g. tuberculosis, syphilis
Sheehan’s syndrome (post partum pituitary necrosis)
What can pituitary hormone deficiency cause?
Functioning pituitary tumour?
Prolactinoma
Acromegaly and Gigantism
Cushing’s Disease
What is prolactin microadenoma?
Galactorrhoea in prolactinoma
What are prolactinomas?
More common in women
Present with galactorrhoea / amenorrhoea / infertility
Loss of libido
Visual field defect
Treatment dopamine agonist eg Cabergoline or bromocriptine.
What are some growth hormone disorders?
gigantism/short stature
What is cushings syndrome?
Causes of cushings syndrome?
Que for patients with pituitary tumour?
Patients with a pituitary tumour:
Is it pressing on optic chiasm?
Are they hypopituitary?
Do they have a functioning tumour?
Benefits of MRI?
Preferred imaging study for the pituitary
Better visualization of soft tissues and vascular structures than CT
No exposure to ionizing radiation
T1-weighted images produce high–signal intensity images of fat. Structures such as fatty marrow and orbital fat show up as bright images.
T2-weighted images produce high-intensity signals of structures with high water content, such as cerebrospinal fluid and cystic lesions
CT
Better at visualizing bony structures and calcifications within soft tissues
Better at determining diagnosis of tumors with calcification, such as germinomas, craniopharyngiomas, and meningiomas
May be useful when MRI is contraindicated, such as in patients with pacemakers or metallic implants in the brain or eyes
Disadvantages of CT
Disadvantages include:
less optimal soft tissue imaging compared to MRI
use of intravenous contrast media
exposure to radiation
Craniopharyngioma
Arise from squamous epithelial remnants of Rathke’s pouch
Adamantinous: cyst formation and calcification
Squamous papillary: well circumscribed
Benign tumour although infiltrates surrounding structures
Peak ages: 5 to 14 years; 50 to 74 years
Solid, cystic, mixed, extends into suprasellar region
Raised ICP, visual disturbances, growth failure, pituitary hormone deficiency, weight increase
Rathke’s cyst
Derived from remnants of Rathke’s pouch
Single layer of epithelial cells with mucoid, cellular, or serous components in cyst fluid
Mostly intrasellar component, may extend into parasellar area
Mostly asymptomatic and small
Present with headache and amenorrhoea, hypopituitarism and hydrocephalus
Meningioma
Commonest tumour of region after pituitary adenoma
Complication of radiotherapy
Associated with visual disturbance and endocrine dysfunction
Usually present with loss of visual acuity, endocrine dysfunction and visual field defects
T1 MRI images similar to grey matter, hypointense to pituitary and enhance with contrast
Lymphocytic Hypophysitis
Inflammation of the pituitary gland due to an autoimmune reaction
Lymphocytic adenohypophysitis
Lymphocytic infindibuloneurohypophysitis
Lymphocytic panhypophysitis
Incidence 1 per 9 million based on pituitary surgery
LAH commoner in women - 6:1
Age of presentation of LAH women: 35 years; men: 45 years
Pregnancy or postpartum
LH imaging
Hypointense on T1 imaging
Hyperintense on T2 imaging
Stalk enlargement
Pituitary enlargement
NFPA/SPA stats
Pituitary adenomas account for <10 – 15% of primary intracranial tumours
NFPA account for 14 - 28% of clinically relevant pituitary adenomas and 50% of pituitary macroadenomas - Preop
Most SPA express gonadotropins or subunits - Postop
23% of SPA are classified as null cell adenomas
NFPA
Diagnosed between 20 and 60 years of age in 78% of cases
50% of NFPA are incidentalomas
50% of macroadenomas have visual disturbances and 50% have headaches
Signs of aggressiveness
Large size
Cavernous sinus invasion
Lobulated suprasellar margins
Non-functioning tumours
No specific test but absence of hormone secretion
* Could have normal pituitary function
* Trans-sphenoidal surgery if threatening eyesight or progressively increasing in size
Hypopituitarism epidemiology
Prevalence 45 cases per 100, 000
Incidence 4 cases per 100, 000
Mortality is high for untreated hypopituitarism
Lower health status, increased incapacitation and sick days
Pituitary tumours/lesions, radiotherapy, head injury, glucocorticoids/opioids, apoplexy
Hypopituitarism clinical manifestations
Depends on which pituitary hormone is deficient
Fatigue
Weight changes
Impaired sleep, pallor, dry skin
Blood pressure changes
Metabolic changes –hyperlipiaemia, insulin resistance, hypoglycaemia
Bowel changes
Sexual dysfunction, amenorrhoea
Polyuria
Testing pituitary function
Complex because:
Many hormones: GH, LH/FSH, ACTH, TSH and ADH
May have deficiency of one or all and may be borderline
Circadian rhythms and pulsatile
- Guiding principle:
If the peripheral target organ is working normally the pituitary is working
Testing pituitary thyroid axis
Primary Hypothyroid - Raised TSH low Ft4
Hypopituitary - Low Ft4 with normal or low TSH
Graves disease (toxic) - Suppressed TSH high Ft4
TSHoma (very rare) - High Ft4 with normal or high TSH
Hormone resistance - High Ft4 with normal or high TSH
Measure Ft4 in pituitary disease
Testing gonadal axis for men
Primary Hypogonadism - Low T raised LH/FSH
Hypopituitary - Low T normal or low LH/FSH
Anabolic use - Low T and suppressed LH
Measure 0900h fasted T and LH/FSH in pituitary disease
Testing gonadal women
Before puberty - Oestradiol very low/undectable with low LH and FSH although FSH slightly higher than LH
Puberty - Pulsatile LH increases and oestradiol increases
Post menarche - Monthly menstrual cycle with LH/FSH, mid-cycle surge in LH and FSH and levels of oestradiol increase through cycle
Primary ovarian failure (includes menopause) - High LH and FSH with FSH greater than LH and low oestradiol
Hypopituitary - Oligo or amenorrhoea with low oestradiol and normal or low LH and FSH
Testing the HPA Axis
Circadian Rhythm
Measure 0900h cortisol and synacthen
Primary AI: Low cortisol, high ACTH, poor response to Synacthen
Hypopituitarism: Low cortisol, low or normal ACTH, poor response to synacthen
Testing GH/IGF1 axis
- GH is secreted in pulses with greatest pulse at night and low or undetectable levels between pulses
-GH levels fall with age and are low in obesity - Measure: IGF-I and GH stimulation test
. Insulin stress test
. Glucagon test
. Other
Prolactin levels
Prolactin under negative control of dopamine
Prolactin is a stress hormone
Measure prolactin or cannulated prolactin (3 samples over an hour to exclude stress of venepuncture
Prolactin may be raised because of:
Stress
Drugs: antipsychotics
Stalk pressure
Prolactinoma
Dynamic Testing
Dynamic stimulation/suppression testing may be useful in select cases to further evaluate pituitary reserve and/or for pituitary hyperfunction
Dexamethasone suppression testing – Cushing’s
Oral glucose GH suppression test - Acromegaly
CRH stimulation – Cushing’s
TRH stimulation – TSHoma
GnRH stimulation – gonadotrophin deficiency
Insulin-induced hypoglycemia – GH/ACTH deficiency
Glucagon test – GH deficiency
Pituitary Hormone Replacement
Adrenal Insufficiency
Hypothyroidism
Growth Hormone deficiency
Hypogonadism
Vasopressin deficiency
??
missed slide 32-35
Thyroxine replacement
Dose 1.6 micrograms/kg/day
Aim to achieve levels to mid to upper half of reference range
Check level before levothyroxine dose
Higher doses usually required in patients on oestrogens or in pregnancy
Growth Hormone Replacement
< 60 years – start 0.2 – 0.4mg/day
> 60 years – start 0.1 – 0.2 mg/day
Aiming for mid-range IGF1 levels
Measure IGF1 6 weeks after dose start and change
Improves lipid profiles, body composition and bone mineral density
Assess QOL
Testosterone Replacement
Different types of formulations: gels, injections, oral
Follow Testosterone levels, Full Blood Count and Prostate Specific Antigen
Improve bone mineral density, libido, sexual function, energy levels and sense of well being, muscle mass and reduce fat
Oestrogen Replacement
Oral oestrogen or combined oestrogen/progestogen formulations (also transdermal, topical gels, intravaginal creams)
Alleviate flushes and night sweats; improve vaginal atrophy
Reduce risk of cardiovascular disease, osteoporosis and mortality
Breast cancer risk, thromboembolism, gall stones, effects on liver and lipids, hyperprolactinemia
Desmopressin
Different formulations: subcutaneously, orally, intra-nasally, sub-lingualy
Adjust according to symptoms
Monitor sodium levels
Trans-sphenoidal Surgery
Complications
Rare
Meningitis
CSF leakage
Stroke
Vascular injury
Septal perforation
Wound infections
Hypopituitarism in 30 to 70%
Are outcomes imp? (stats slide 41 missed)
Radiotherapy
Treatment of resistant macroadenomas after medical and surgical treatment fails
Conventional, fractionated
Slow response up to 5 to 10 years; achieves control in 93%; prevents tumour progression in 75 to 90%
Ideal for significant suprasellar extension, <5mm clearance from optic apparatus, size , poor tumour definition
High rate of hypopituitarism (50%)
Optic nerve damage, radionecrosis of brain tissue, seizures, CVA, malignancy
Stereotactic gamma knife surgery
Achieves control in 83 to 97% and tumour regression in 42 to 78%
High rate of hypopituitarism (0-36%) but probably less side effects
Radiation to narrow focused area
Cavernous sinus invading tumours
