Chapter-5 Endocrinology Flashcards
Name three thyroid hormones
Thyroxine (T4)
Triiodothyronine (T3)
Calcitonin
How are the thyroid hormones released (T4 & T3)
Hypothalamus secretes thyroid releasing hormone which stimulates the release of thyroid stimulating hormone from the anterior pituitary which obviously stimulates the release of T3 and T4 from the thyroid
What’s the problem with non-functioning pituitary tumours?
Cause problems but don’t produce hormones to detect it
Do functioning pituitary tumours produce hormones to detect it?
Yeh
When May pituitary infarction occur and why is it rare?
Someone’s post pregnancy, rare because it has a good blood supply
How can pituitary tumours cause visual problems
Where they press is where the retinal nerves cross, this causes visual field loss
What is the treatment for non-functional tumours
There is no pharmacological treatment just surgery: aim is to protect eyesight and restore pituitary function
What’s the most common functioning pituitary tumour
Prolactinomas
What is a prolactinoma?
Prolactin secreting tumours
What’s the role of prolactin
Acts as a contraceptive and post pregnancy
Symptoms of prolactinoma in women
Pressure effects (headache, vision)
Absent periods
Infertility
Galactorrhoea
Symptoms of prolactinoma in men
Pressure effects (headache, vision) Erectile dysfunction Hypogonadotrophic Hypogonadism
What’s the rationale for using dopamine receptor agonists in prolactinomas
Prolactin is inhibited by release of dopamine from the hypothalamus
Name two ergot derived dopamine agonists used in prolactinomas
Cabergoline
Bromocriptine
Name a non-ergot derived dopamine agonist used in prolactinomas
Quinagolide
What are the problems with using dopamine agonists in prolactinomas
Concerns over valvular and retroperitoneal fibrosis (require baseline then annual echo)
When treating a woman with prolactinoma who wants to get pregnant which dopamine agonist is used and why
Bromocriptine is preferred because cabergoline has a long half life
What is acromegaly?
Growth hormone secreting pituitary tumours–> teeth separating, jaw growing, large lips, nose, hands
What is used to treat acromegaly
First line surgery
Somatostatin analogues may achieve control of growth hormone secretion
Name two somatostatin analogues used to treat acromegaly and what is their half life?
Octreotide
Lanreotide
Half life: 2hrs
What is somatostatin and what is it’s half life
Growth hormone inhibitory hormone
2 minutes!
To monitor patients with acromegaly response to somatostatin analogues what should you measure and why not GH?
Measure IGF-1
Because GH goes up and down throughout the day
What’s the only available growth hormone receptor antagonist
Pegvisomont
How do you monitor pegvisomont effects
IGF-1
Symptoms of cushings
Moon face Buffalo hump Bruising and thin skin Lemon in match stick Hypertension Diabetes Low potassium Gastric ulcers
How do you treat cushings
Surgery
Metyrapone: cortisol synthesis inhibitor before surgery
Which bit of pituitary is more robust?
Posterior
What age do you reach peak bone mass
25
Who qualifies for growth hormone?
Must have proven underlying pathology- stimulation test must prove GH deficiency, low QoL AGDA score
3-9month trial with definite improvement in QoL AGDA
Patient has active malignancy should you give growth hormone replacement
NO - contraindicated
List side effects of growth hormone replacement
Peripheral oedema Arthralgia Carpal tunnel syndrome Globular tolerance Benign intracranial hypertension
What is polycythaemia
Testosterone stimulates RBC production in bone marrow, raised hematocrit and Hb can cause strokes
Is hydrocortisone long acting and how often is it given and why
No it’s short acting, given TDS to mimic natural diurnal rhythm
When is cortisol highest?
Morning
Why do you double dose of hydrocortisone in hospital?
Stressed - need to mimic this - cortisol is stress hormone
A drop in hydrocortisone for at least 6 hrs can lead to what?
Adrenal crisis: drop BP
What are the hydrocortisone sick day rules
Double dose if:
- febrile illness
- fractured limb
- severe shock
- long haul flight
- surgery: IV then double dose
- gastroenteritis: IM double dose
- dental extraction 20mg
How does desmopressin work
Acts on kidney collecting ducts and tubules (ADH) to allow water reabsorption into the bloodstream
What two hormones does the posterior pituitary gland release
ADH
Oxytocin
Name 6 hormones the anterior pituitary releases
ACTH GH MSH TSH Gonadotropins (FSH,LH)
If someone has impaired thyroid hormones levels what do you need to determine
Cause:
Primary- thyroid
Secondary- pituitary
Tertiary- hypothalamus
What’s the role of the thyroid hormones?
Involved in metabolism
Growth and development
List the signs of hypothyroid
Facial swelling Hair loss Dry skin Reduced heart rate Husky voice Hypothermia Goitre
Give signs of hyperthyroid
Tremor Warm skin Agitation Goitre Exophthalmos Atrial fibrillation
Can hyperthyroidism cause atrial fibrillation?
Yeh!
What’s the half life of T4
5-7 days
What’s the half life of T3
1day
True or false: primary hypothyroidism is diagnosed using thyroid hormone levels (low) and TSH (high)
True
What is exophthalmos and what is it a sign of
Bulging of the eye - hyperthyroid
What is Graves’ disease and what does it cause
Autoimmune condition causing hyperthyroid (thyrotoxicosis)
True/false: secondary hypothyroidism TSH would be high
False it would be low
Give four causes of primary hypothyroid
Hashimoto’s thyroiditis (autoimmune)
Anti-thyroid meds
Thyroidectomy
ADR to amiodarone
List symptoms of hypothyroid
Fatigue Constipation Weight gain Depression Menorrhagia Psychosis Hearing loss
Give symptoms of hyperthyroid
Palpitations Diarrhoea Weight loss Sweating Heat intolerance Hunger and thirst Anorexia
Which thyroid hormone is active in stimulating cells
T3
How do organs in the body that require thyroid hormones obtain it?
They have the ability to generate T3 by converting T4 by enzymes called deiodinases
Levothyroxine is a synthetic form of what?
Thyroxine (T4)
What are the main treatments for hyperthyroidism
1) medication to stop it producing too much thyroid hormone
2) radioiodine treatment
3) surgery
Name two thionamides used to treat hyperthyroid
Carbimazole
Propylthiouracil
When taking thionamides do you see the benefit immediately?
No after 1 or 2 months
What is used to relieve symptoms of hyperthyroid whilst waiting for thionamides to work
Beta-blocker
How does carbimazole work
Inhibits the organification of iodide and hence the synthesis of thyroid hormones. Also has mild immunosuppressive activity that reduces serum level of TSH receptor antibody
Two drugs that can cause drug induced thyroid disease
Amiodarone
Lithium
How can amiodarone cause drug induced thyroid disease
It inhibits the conversion of T4 to T3 and also it contains 40% iodine which can directly inhibit thyroid function (hypo) alternatively it can cause hyper via an inflammatory process
True/false: cholestyramine can reduce the absorption of thyroxine
True
True or false: ferrous sulphate can increase the absorption of thyroxine
False it reduces it
Do glucocorticoids decrease TSH secretion?
Yeh
Does amiodarone have a long half life? How should you manage hyper and hypo thyroid on amiodarone?
Hypo- start levothyroxine
Hyper- stop amiodarone because carbimazole won’t work for some reason
How does lithium cause hypothyroidism
1) increases intrathyroidal iodine content
2) inhibits coupling of iodotyrosine residues to form T3 and T4
3) inhibits release of T4 and T3
List patients which you should screen for thyroid condition
Amiodarone/lithium Diabetes AF Hyperlipidaemia Down's syndrome Turners syndrome Addison's disease
What does the adrenal medulla produce
noradrenaline
Adrenaline
What is Cushing’s syndrome
Cushings disease (tumour) Exogenous steroid intake
What is Addison’s disease
Lack of cortisol or mineralocorticoid
What is conns syndrome
Hyperaldosteronism
What is phaeocromocytoma
Tumour that causes excess release of adrenaline and noradrenaline
What does the adrenal cortex produce
Steroids:
Corticosteroids
Mineralocorticoids
Sex hormones
Symptoms of addisons
Anorexia Weight loss Weakness DiZzy and low BP Arthralgia Low Na high K No fight or flight
In Addison’s- to replace mineralocorticoid what should you give
Fludrocortisone
In Addison’s what should you give for glucocorticoid replacement
Hydrocortisone
How to diagnose cushings
PMH
Dexamethasone test
Symptoms
In primary hypothyroidism why are TSH levels often high?
Cos low levels of T3 and T4 feed back to hypothalamus
Advantages and disadvantages of block and replace for hyperthyroid treatment
Negative: more tablets
Positive: quicker onset
What monitoring is required for carbimazole
Fever Sore throat Bruising bleeding WCC Signs of infection
If hyperthyroid in pregnancy can you use block and replace?
NO just carbimazole
