Rest of endocrine Flashcards
In primary hypogonadism (men) testosterone and LH/FSH would be:
Testosterone would be low.
LH/FSH would be raised.
In hypopituitarism (men) testosterone and LH/FSH would be:
Testosterone is low.
LH/FSH can be normal or low.
In anabolic testosterone use (men) testosterone and LH/FSH would be:
Testosterone would be low.
LH/FSH suppressed.
What type of blood test would be required in pituitary disease for men?
09:00h fasted T and LH/FSH test
What would a pre-puberty blood panel look like for a woman (gonadal axis)?
Oestradiol low/undetectable
Low LH and FSH (FSH>LH)
What would the blood test for a woman at puberty look like (gonadal axis)?
Pulsatile LH secretion increases
Oestradiol increases
What would the blood test for a post menarche woman look like (gonadal axis)?
Monthly menstrual cycle:
LH and FSH surge in the middle of the cycle
Oestradiol levels increase throughout the cycle
What would the blood test for a woman with primary ovarian failure look like (including menopause)?
Oestradiol would be low.
LH and FSH would be high (FSH>LH).
What would the blood test for a woman with hypopituitary disease would look like?
Oligo- or amenorrhoea with low oestradiol.
Normal or low LH and FSH.
What time do we measure cortisol levels?
09:00h in the morning and synachthen.
Primary AI:
Cortisol: low
ACTH: high
Response to synachthen test: poor
Hypopituitarism in AI:
Cortisol: low
ACTH: low or normal
Response to synachthen test: poor
When is the greatest pulse of GH secreted?
At night – followed by low or undetectable levels between pulses.
In what conditions does GH level fall?
With ageing and in obesity.
How do we measure the GH/IGF-1 axis?
Measuring IGF-1 and GH stimulation test:
> Insulin stress test
> Glucagon test
> Other
What is unique about measuring prolactin levels?
It is under negative control of dopamine.
It is a stress hormone.
Why prolactin levels may be raised?
Stress
Drugs: antipsychotics
Stalk pressure
Prolactinoma
How to measure prolactin?
Can measure prolactin or cannulated prolactin (3 sampled over an hour to exclude stress of venepuncture).
Nephrogenic DI
= Vasopressin resistance (there is hormone secretion but no response)
Cranial DI
= Vasopressin deficiency (no ADH is being made or secreted)
What test is used to investigate vasopressin deficiency/resistance?
Water deprivation test with desmopressin.
What other molecule can be measured to confirm Dx of DI?
Copeptin
Primary polydipsia is confirmed if stimulated copeptin levels are:
> 4.9 pmol/L
What dynamic testing is used in Cushing’s?
Dexamethasone suppression testing.
CRH stimulation.
What dynamic testing is used in acromegaly?
Oral glucose GH suppression test.
What dynamic testing is used in TSHoma?
TRH stimulation.
What dynamic testing is used in gonadotrophin deficiency?
GnRH stimulation
What dynamic testing is used in GH/ACTH deficiency?
Insulin induced hypoglycaemia.
What other dynamic testing can be used in GH deficiency?
Glucagon test.
What is the preferred imaging study for the pituitary?
MRI
Why is MRI chosen to study the pituitary?
Better visualisation of soft tissues and vascular structures than CT.
No exposure to ionising radiation.
T1-weighted images produce high-signal intensity images of what?
Fat – Structures such as fatty marrow and orbital fat show up as bright images.
T2-weighted images produce high-intensity signals of what structures?
Structures that have high water content (CSF and cystic lesions).
CT imaging gives better visualisation of what?
Bony structures and calcifications within soft tissues.
What type of tumours are better Dx with CT?
Tumours with calcification such as germinomas, craniopharyngiomas and meningiomas.
In what patient groups would CT be useful?
PT with pacemakers or metallic implants in the brain or eyes.
What are some of the disadvantages of CT?
Suboptimal soft tissue imaging compared to MRI.
Use of IV contrast is required.
Exposure to radiation.
GH deficiency results in:
Short stature.
Abnormal body composition.
Reduced muscle mass.
Poor quality of life.
Rx of GH deficiency?
Exogenous GH.
LH/FSH deficiency results in what?
Hypogonadism
Reduced sperm count
Infertility.
Menstruation problems.
Rx of LH/FSH deficiency?
Rx of LH/FSH deficiency?
Testosterone in males.
Oestradiol and progesterone in females.
TSH deficiency results in what?
Hypothyroidism.
Rx of TSH deficiency?
Levothyroxine
ACTH deficiency results in what?
Adrenal failure and decreased pigmentation
Rx of ACTH deficiency?
Hydrocortisone.
ADH deficiency results in what?
Vasopressin deficiency = DI
Rx of ADH deficiency?
DDAVP
What is a challenge in drug delivery?
The gut length and transit time. This was overcome by using modified release microparticulates
Thyroxine replacement therapy?
Dose 1.6 micrograms/kg/day.
Aims to achieve the mid to upper half reference range.
Higher doses are required in pregnancy and in patients on oestrogen.
GH replacement therapy?
<60 years – start 0.2-0.4 mg/day
>60 years – start 0.1-0.2 mg/day
Aiming for mid-range IGF1
Measure IFG1 6 weeks after dose start and adjust.
Improves lipid profiles, body composition and bone mineral density.
Testosterone replacement therapy?
Different formulations (gels, injections, oral.
Follow testosterone levels, FBC, PSA.
Improve bone mineral density, libido function, energy levels, sense of well-being, muscle mass and reduce fat.
Oestrogen replacement therapy?
Oral oestrogen or combined oestrogen/progesterone formulations (transdermal, topical gels, intravaginal creams).
Alleviate flushes and night sweats, improve vaginal atrophy.
Reduce risk of CVD, osteoporosis and mortality.
Desmopressin therapy?
Desmopressin therapy?
Different formulations: SC, PO, intra-nasally, SL
Adjust dose according to symptoms.
Monitor sodium levels
What are the consequences of excess growth hormone production?
Excess growth hormone goes to the liver where it gets transformed into IGF-I which affects cartilage and bone growth.
Two forms depending on onset of age (gigantism or acromegaly).
What is the incidence of acromegaly?
3.3 per a million
What is the mean age at diagnosis?
44 years. (38-69)
What is the mean duration of symptoms?
8 years. (7-11).
What are the co-morbidities with acromegaly?
Hypertension and heart disease.
Sleep apnea.
Insulin-resistant diabetes.
Arthritis.
Cerebrovascular events and headaches.
What is the impact of acromegaly on survival?
Overall survival is reduced by ~10 years.
26-50% die before 50 years.
64-89% die before 60 years.
Both diabetes and cardiac disease have a significant impact.
How is acromegaly diagnosed?
Presence of clinical features.
GH levels.
IGF-I levels.
What are the common presenting features of acromegaly?
Acral enlargement.
Arthralgias.
Maxillofacial changes.
Excessive sweating.
Headache.
Hypogonadal symptoms.
What test is used to diagnose acromegaly?
75g oral glucose tolerance test.
When is acromegaly excluded?
If random GH <0.4 ng/mL and IGF-I is normal.
If IGF-I is normal and GTT nadir (low point), GH <1 ng/ml.
What are the objectives of therapy?
Restoration of basal GH and IGF-I to normal levels.
Relief of symptoms.
Reversal of visual and soft tissue changes.
Prevention of further skeletal deformity.
Normalisation of pituitary function.
What are the options for treatment of acromegaly?
Pituitary surgery.
Medical therapy.
Radiotherapy.
Transsphenoidal surgery is used for all types of pituitary adenomas except for what?
Prolactinoma.
What makes the transsphenoidal surgery challenging?
Large size of the tumour.
Invasiveness.
What is the differentiating point for microadenomas vs. macroadenomas?
10mm.
Microadenoma <10 mm and the surgical cure rate is ~90%.
Macroadenoma >10 mm and the surgical cure rate is <50%.
What are the two important determinants of success of a surgery?
The size of the tumour.
The surgeon
What are the complications of pituitary surgery?
There is a long list, but the two important ones are hypopituitarism and death.
What are the different types of radiotherapies?
Conventional (multi-fractional).
Stereotactic (single fraction, less radiation to surrounding tissues).
What are the examples of stereotactic radiotherapy?
Gamma knife.
LINAC.
Proton beam.
Sheffield is the National Centre for what?
Stereotactic Radiosurgery.
What are the problems with radiotherapy?
Loss of pituitary function in the long term.
Potential damage to local structures (eye nerves).
Control of tumour growth/excess hormone secretion is not always achieved.
Life-long monitoring needed for all patients.
What two factors determine the efficacy of conventional radiotherapy?
GH level.
The extension of the tumour.
What are the disadvantages of conventional radiotherapy?
Delayed response.
Hypopituitarism.
Rare secondary tumours.
Rare visual defects.
What medical therapies are used for the treatment of acromegaly?
Dopamine agonists – cabergoline.
Somatostatin analogues.
GH receptor antagonist.
What are the goals of dopamine agonists therapy?
Control GH.
Control IGF-I.
Improve well-being.
What are the advantages of Cabergoline over bromocriptine?
More potent.
Fewer side effects.
Twice weekly dosage.
What are the advantages of dopamine agonist therapy?
No hypopituitarism.
Oral administration.
Rapid onset.
What are the disadvantages of dopamine agonist therapy?
Relatively ineffective.
Side effects.
Dopamine agonists are particularly useful in what tumours?
GH + prolactin co-secreting tumours.
Occasional dramatic tumour shrinkage.
Control of GH secretion.
Describe the function of human somatostatin:
Inhibits multitude of hormones.
Half-life is short ~3 minutes.
Rebound.
Binds all 5 receptor subtypes.
Synthetic version of somatostatin analogues.
More specific.
Half-life is extended 100 mins.
No rebound.
Examples: Octreotide and Lanreotide
What are the goals of somatostatin analogues?
Control GH.
Control IGF-I.
Clinical improvement.
Somatostatin analogues control what?
IGF-I 65%.
GH 60%.
Tumour shrinkage.
What are the determinants of efficacy in somatostatin analogues?
GH level.
Tumour size.
SMS receptor expression.
What are the disadvantages of somatostatin analogues?
Injectable.
Side effects.
Describe Pegvisomant:
GH analogue.
191 AAs.
9 AA substitution.
4-5 PEG moieties.
Half-life >70 hours.
SC administration.
What are the disadvantages of Pegvisomant use?
Serum GH cannot be used as disease marker.
Cross reacts in GH assays.
What is the incidence of prolactinoma?
10 per 100.000
Which gender is more affected by prolactinomas?
Women»_space; men.
What is the prevalence of prolactinomas?
90 per 100.000.
What is a prolactinoma?
Lactotroph cell tumour of the pituitary.
What are the local effects of the tumour (macroadenoma)?
Headache.
Visual field defect – bitemporal hemianopia.
CSF leak (rare).
What are the effects of prolactin?
Menstrual irregularity/amenorrhoea.
Infertility.
Galactorrhoea.
Low libido.
Low testosterone in men.
Hyperprolactinaemia can be caused by:
Macroprolactinoma (can be massive).
Microprolactinoma (virtually always stay small).
Non-functioning pituitary tumour – compression of the pituitary stalk (prolactin <4000 mlU/L).
Antidopaminergic drugs.
Other causes (stress, hypothyroidism, PCOS, drugs, renal failure, chest wall injury).
Management of prolactinomas?
Medical rather than surgical.
Dopamine agonists (cabergoline, bromocriptine, quinagolide).
Remarkable shrinkage usually with macroadenomas (sight saving).
Microadenomas usually respond to small doses of cabergoline (1x, 2x a week).
There are different definitions of Diabetes, discuss this.
Symptomatic presentation and random plasma glucose is greater than or equals to 11.1 mmol/L.
Fasting plasma glucose is greater than or equals to 7.0 mmol/L.
HbA1c is greater than or equals to 48 mmol/mol.
No symptoms – OGTT (75g glucose), fasting levels are greater than or equals to 7 or 2 hour value is greater than or equals to 11.1 mmol/L.
What are the presenting features of diabetes?
Thirst: osmotic activation of the hypothalamus.
Polyuria: osmotic diuresis.
Weight loss and fatigue: lipid and muscle loss due to unrestrained gluconeogenesis.
Hunger: lack of useable energy source.
Pruritis vulvae and balanitis: vaginal candidiasis + chest and skin infections.
Blurred vision: altered acuity due to uptake of glucose/water into lens.