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Endocrinology Flashcards

1
Q

Describe the Hypothalamus- Pituitary- Thyroid (HPT) Axis

A

The hypothalamus makes TRH
TRH travels to the pituitary and stimulates it to make TSH
TSH goes to the thyroid gland which then produces T3/4

T4 negatively feedbackst to the hypothalamus and pituitary

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2
Q

What is the treatment of hypothyroidism?

A

T4 (levothyroxine) (50-200 mcg/ day)

Adjust thyroxine to keep TSH normal

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3
Q

What does TSH/ TRH do in primary Hypothyroidism?

A

Elevation

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4
Q

What are hypothyroidism treatment problems?

A

> Levothyroxine may worsen IHD symptoms- helped by gradual introduction
Excessive thyroxine (reduced TSH causes osteopaenia and AF)
T3 has no evidence base due to short half life and fluctuating

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5
Q

What are the causes of thyrotoxicosis?

A 
High uptake
> Graves (most)
> Toxic multinodular goitre (RI first)
> Single toxic adenoma (RI first)
> (TSH induced, functioning thyroid cancer, trophoblastic tumour and struma ovarii)

Low uptake
> Subacute thyroiditis
> Postpartum thyroiditis
> Amiodarone
> Silent thyroiditis
> Factitious thyroiditis
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6
Q

How do you differentiate the causes of thyrotoxicosis?

A

Technetium scan

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7
Q

How do you treat low uptake thyrotoxicosis?

A

> Beta blockers

> NOT thionamides

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8
Q

How do you treat high uptake thyrotoxicosis?

A 
> Beta blockers
> Thionamides
> Iodine 
> Surgery
> Radio iodine
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9
Q

What beta blockers can be used?

A

Propranolol
Atenolol
Nadolol
Esmolol

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10
Q

What are the thionamides?

A

Carbimazole

Propylthiouracil

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11
Q

What do thionamides do?

A

Block the organification of iodine

Ability to stick iodine onto tyrosine residues

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12
Q

What does perchlorate do?

A

Blocks the iodine sodium co transporter

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13
Q

What are the side effects of thionamides?

A

> Rash

> Agranulocytosis (clinical diagnosis with fever not routine bloods) [RARE]

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14
Q

How can carbimazole be prescribed?

A

> Titration

> Block and replace

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15
Q

How do we use Radioiodine?

A

> Cancer
NOT if tracheal compression goitre or thyroid eye disease
Can precipitate thyroid storm
Can cause hypothyroid

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16
Q

How does ADH affect water balance?

A

The hypothalamus tests the osmolality, if it is high, ADH is released which reabsorbs water from the collecting duct. This lowers osmolality whilst also contributing to renal blood flow and causing the activation of RAAS.

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17
Q

What happens if there is a lack of ADH (Diabetes Insipidus)?

A

Low ADH = High water in urine and increased Osmolality

This causes thirst to maintain homeostasis

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18
Q

What happens in water depravation in DI?

A

Dangerous Hypernatraemia

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19
Q

How does ADH work on the CD?

A

ADH interacts with V2 causing protein kinases to align allowing micelles of water to get into the capillary from water

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20
Q

How do we replace ADH?

A

> DDAVP nasal spray at 5-100 micrograms a day OR parenterally (0.1-2.0 microgm) OR Oral (100-1000 Microgm)
Dilutional hyponatraemia avoided by polyuria episode

21
Q

How do you diagnose Acromegaly?

A

> OGTT
GH series
IGF 1 for longer term control

22
Q

How do you treat acromegaly?

A

> Surgery for pit. tumours
Radiotherapy (adjunct)
Somatostatin analogues

23
Q

Why are dopamine agonists no longer used in Acromegaly?

A

> 10% normalised
SE- headaches, postural hypotension
Doesn’t affect tumour size in acromegaly

24
Q

What are the somatostatin analogues?

A

Octreotide (Daily)
Lanreotide (Once a month)
Sandstatin (Once a month)

25
What are the side effects of somatostatin analogues?
GI side effects | Gallstones
26
What are the GH antagonists?
Pegvisomant Modified recombinant GH Reduced signal transduction IGF1 normalised in 90$
27
Why is GH replacement given?
In children For growth velocity, sex steroids and final heights In adults Wellbeing, short term memory, reduced depression, bone turnover reduced, improves insulin sensitivity and CV risk, also muscle bulk and power
28
How do you measure testosterone?
9 am testosterone
29
How do you replace testosterone?
``` Oral Restandol (liver metabolism) IM sustanon (variable) IM Nebido- 3 monthly IM Transdermally- may cause local reaction Always monitor symptoms to see improvement ```
30
How do you deal with erectile dysfunction?
Sildenafil and alprostadil
31
How does prolactin get released?
TRH causes prolactin release from pituitary Dopamine from hypothalamus work on D2 receptors on lactotrophs and reduces prolactin secretion Prolactin works in conjunction with oxytocin to cause milk let down
32
How do we use D2 receptors?
Reduces prolactin secretion and cytoplasm Can cause tumour shrinkage Pt may need high dose for long time but often are fine with low dose
33
How does bromocriptine and cabergoline work?
Stimulates D2 and reduces prolactin
34
What are the features of bromocriptine?
> Semisynthetic ergot alkaloid (1mg/ day) > Dizziness, nausea and malaise are SE > Increase dose weekly
35
What are the features of Cabergoline?
125 mcg to 2 mg a week (divided at higher doses)
36
How do we replace glucocorticoids?
Hydrocort 10 mg morning, 5mg at lunch, 5 mg in the evening Increase if illness Pt may carry medicalert
37
How does cortisol vary daily?
Morning is high
38
How does excess steroids present?
``` Cushingoid facies Interscapular fat pad Thin skin Bruise Central adiposity Hyperglycaemia High cholesterol Striae Leukocytopaenia Polythaemia Infections Hypertension Hypernatraemia and hypokalaemia Osteoporosis Stomach ulcers Psych changes Irregular periods and infertility Hirsutism ```
39
How does steroid deficiency present?
``` Dark (If adrenal problem) Pale (If pit. probelm) Weight loss Weakness Hypoglycaemia Small infections become worse Postural hypotension Tired all the time Infertility Loss of hair ```
40
Why do we need cortisol?
> Fever > disease > Injury
41
What do we do with intercurrent stress?
If eating: > Treble normal dose three days and doouble for 3 days If vomiting: > 100 mcg parenterally
42
How do you treat Cushing's?
Metyrapone | Ketoconazole
43
What is the MOA of metyrapome?
``` Blocks final step in cortisol Sx 80% response Cushing's disease Short duration of action andrigens, 11-DOC BLock and replace ```
44
How does aldosterone work?
Works in DCT Acts in nucleus of cell (MC receptor) Causes reabsorption of sodium and excretion of H ions and K and bicarb production
45
How do you replace mineralocorticoids?
Fludrocortisone (50-200 Microgm) Daily Excess may cause hypertension May adjust with plasma renin activity Only needed in primary adrenal failure
46
Fill in the blank: | High GC has some ________ effects
Mineralocorticoid
47
How do you treat a Conn's adenoma?
Surgery Spirinolactone/ amiloride (if hyperplasia) K+ replacement
48
What odes eplerenone do?
> Blocks aldosterone at MC receptor > Avoid if hyperkalaemia > Increased renin and aldosterone > No gynaecomastia

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