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Thyroid, pituitary and adrenal Flashcards

1
Q

What does the thyroid do?

A

→ Secretes thyroxine (T4) and triiodothyronine (T3) stimulated by TSH from the pituitary gland
→ Thyroid hormone production is regulated by hypothalamic thyrotropin-releasing hormone (TRH) which stimulates pituitary thyrotropin (TSH)
→ Protein thyroglobulin (Tg) is used by thyroid to produce T3 and T4
→ T3 is the active form. T4 is the prohormone to T3
→ Thyroid gland produces 100% of T4 but only 20% of T3 (80% in produced by conversion of T4 to T3 in peripheral tissues)

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2
Q

What are the thyroid hormone binding proteins?

A

→ Thyroxine binding globulin (TBG), pre-albumin (transthyretin) and albumin
→ Most of T4 and T3 are protein bound
The unbound free T3 and T4 (FT3 and FT4) are active

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3
Q

What is the Wolff-Chaikoff effect?

A

Wolff-Chaikoff effect is an autoregulatory phenomenon, whereby a large amount of ingested iodine acutely inhibits thyroid hormone synthesis within the follicular cells, irrespective of the serum level of thyroid-stimulating hormone (TSH)

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4
Q

What are the symptoms of hypothyroidism?

A 
Weakness
Lethargy
Weight gain
Depression
Feeling cold
Hoarse voice
Menorrhagia
Hair loss
Bradycardia (rare)
Goitre
Erythema ab igne (hot water bottle rash, is a skin condition caused by long-term exposure to heat because these patients feel cold)
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5
Q

What are the symptoms of hyperthyroidism?

A 
Hyperactivity
Irritability
Heat intolerance
Insomnia
Palpitation
Dyspnoea
Diarrhoea
Weight loss
Increased appetite
Polyuria
Polydipsia
Pruritus
Amenorrhoea
Loss of libido
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6
Q

What is the treatment of hyperthyroidism?

A

Carbimazole
· Decreases uptake of inorganic iodine, reducing formation of T3 and T4
· Can convert into methimazole and present thyroid peroxidase enzyme from coupling and iodinating tyrosine residues on thyroglobulin

Propylthiouracil
· Choice of medication in pregnant and lactating women
· Binds to thyroid peroxidase to inhibit iodide to iodine conversion
· Also inhibits T4 to converting into T3
· Preferred in pregnancy due to the lower concentration found in breast milk

Beta blockers: (80mg BD)
· Symptomatic control of anxiety, palpitations and tremor. Also influences monodeiodinaiton
· Propranolol

Radioiodine therapy:
· Radioactive iodine-131 given orally
· Iodine taken up by thyroid glad for use in thyroid hormone synthesis but the radiation emitted destroys over acting thyroid cells

Thyroidectomy:
Total is preferred over partial thyroidectomy due to risk of relapse

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7
Q

Common side effects of the medications used for hyperthyroidism

A

Carbimazole: arthralgia, agranulocytosis, headache, jaundice, malaise, pruritus, taste disturbances, aplasia cutis (congenital disorder)

Propylthiouracil: arthralgia, jaundice, leukopenia, malaise, pruritus, taste disturbances

Beta blockers: SOB and drowsiness

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8
Q

Common side effects of radioiodine therapy and thyroidectomy

A

Radioiodine therapy: normal functioning follicular cells may be destroyed so thyroxine treatment needed after

Thyroidectomy: recurrent laryngeal nerve damage and vocal cord paralysis, hypoparathyroidism, thyroid crisis and local haemorrhage. Long term - formation of keloid scar

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9
Q

What are the symptoms of Addison’s disease?

A

→ Weight loss and anorexia
→ Hyperpigmentation - increased ACTH leads to melanocyte stimulating hormone production
→ Tiredness and weakness
→ Postural hypotension and dizziness
→ Symptomatic hypoglycaemia
→ Hair loss and reduced libido
→ Salt craving - hyponatraemia due to decreased aldosterone production

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10
Q

What are the symptoms of cushing’s disease?

A

entral obesity - buffalo hump, moon face, hirsutism, thinning of hair
→ Hypertension (increased release of aldosterone)
→ Diabetes
→ Weakness of muscles
→ Bruising, scarring, purple striae around abdomen - cortisol inhibits fibroblast proliferation and formation of collagen
→ Thinning of skin and loss of connective tissue to support capillaries - more susceptible to injury
→ Decreases new bone formation (decreases osteoblast function)
→ Inhibition of GRH so ovarian and testicular function is impaired
→ Mood disturbances: labile, depression, insomnia, psychosis
Menstrual changes

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11
Q

What are the investigations done for Addison’s?

A
  • U&Es: hyperkalaemia due to reduced aldosterone production. Hyponatraemia as hyperkalaemia increases action of Na+/K+ pump
  • Serum cortisol and ACTH
  • ACTH syncacthen stimulation test
  • Serum glucose - hypoglycaemia
  • TFTs - cortisol inhibits TRH
  • 24 hour urinary free cortisol
  • Dexamethasone suppression test
  • Adrenal CT
  • FBC - normocytic normochromic anaemia, raised ESR and eosinophilia
  • Prolactin testing
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12
Q

What are the causes for hypothyroidism?

A

Hashimoto’s disease (commonest in developed countries)
Iodine deficiency (commonest in underdeveloped countries)
Drugs (lithium, Amiodarone, Iodine)
Thyroidectomy/radio-iodine therapy
Haemochromotosis

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13
Q

What are the causes of hyperthyroidism?

A 
Graves' disease (TRAb)
Drugs (Amiodarone, oestrogen) 
Toxic nodular goitre
Thyroiditis
TSH secreting tumours
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14
Q

What is the treatment for hypothyroidism?

A

Levothyroxine (1.6 microgram/kg)
Lower dose given to patients with history of ishaemic heart disease
Overtreating can lead to osteoporosis and arrhythmias

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15
Q

What are the differential diagnosis for hypothyroidism?

A

Depression
Anaemia
Dementia

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16
Q

What is myxoedema?

A
  • Rare severe form of hypothyroidism
  • Cutaneous and dermal oedema because of increased deposition of connective tissue. These bind to water and produce non-pitting boggy oedema around eyes, feet, tibia, hands, supraclavicular fossa
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17
Q

How can hypothyroidism be classified?

A

Based on the time of onset: congenital or acquired (1)

The level of endocrine dysfunction:
Primary hypothyroidism - abnormality in thyroid gland itself
Secondary hypothyroidism - secondary to disorders of the pituitary or hypothalamus

The severity:
Overt hypothyroidism - TSH concentration is above the reference range (greater than10mU/L) & serum free T4 levels below the reference range
Subclinical hypothyroidism - serum TSH concentration is increased, serum free T4 concentrations are within the reference range (2)

18
Q

Who gets pretibial myxoedema?

A

Pretibial myxoedema is nearly always associated with Graves disease.

19
Q

What is the classic triad of signs of Graves disease?

A

Pretibial myxoedema
Ophthalmopathy (prominent eyes due to deposition of myxoedema behind the orbit)
Acropachy (swelling of distal digits with overgrown nail plates that may lift off the nail bed; similar to clubbing)

20
Q

Go through the thyroid examination

A
  1. Inspection
    i) Neck from front - goitre
    ii) Asked to swallow - moves up
    1. Palpation
      i) Tenderness - movement with swallowing
      ii) Size (soft/firm/hard) - nodular or diffuse
      iii) Medial edge of SCM - lymph nodes
    2. Percussion
      i) Upper mediastinum - retrosternal goitre
    3. Auscultation
      i) Bruit - inspiratory stridor
    4. Thyroid status
      i) Exophthalmos/proptosis
      ii) Lid retraction/ lid lad
      iii) Conjunctival injection
      iv) Periorbital oedema
      v) Loss of movements
      vi) Myxoedema
      vii) Hyperactivity/restlessness
      viii) Palm - warm/cold/sweaty
21
Q

What are the features of acromegaly?

A

Coarse facial appearance, Spade-like hands
Increase in shoe size
large tongue, prognathism, interdental spaces excessive sweating and oily skin: caused by sweat gland hypertrophy features of pituitary tumour: hypopituitarism, headaches, bitemporal hemianopia
raised prolactin in 1/3 of cases → galactorrhoea
6% of patients have MEN-1

22
Q

Common drug causes of gynaecomastia

A 
spironolactone (most common drug cause)
cimetidine
digoxin
cannabis
finasteride
gonadorelin analogues e.g. Goserelin, buserelin
oestrogens, anabolic steroids
23
Q

How long does Carbimazole take to lower free T4?

A

6 weeks

24
Q

Why is propylthiouracil used more in pregnant women?

A

Doesn’t cross the placental barrier as much.
Carbimazole is a teratogenic and patient needs to be on contraceptive to get it

However PTU is only effective for 75 mins

25
Q

The regimens of giving Carbimazole:

A

Titration therapy (this is initiated with a medium dose of anti-thyroid agent. TFTs are then reviewed after 6-weeks and influence the next dose) and block and replace therapy. (Carbimazole is given initially to induce a euthyroid state, which is then maintained with daily doses of Carbimazole plus thyroxine)

Block and replace should not be used in pregnancy due to the higher doses of Carbimazole used and risk of neonatal hypothyroidism

26
Q

What kind of corticoid is fludrocortisone:

A

Mineralocorticoid

27
Q

Why is hyperprolactinaemia more common in men?

A

In women: presents early due to effects on fertility, disturbance of menstruation, anovulation, galactorrhoea, so that the prolactinoma is often small and confined to the pituitary without disturbance of other hormone production

in men the traditional symptoms of hyperprolactinaemia are often absent and the prolactinoma can grow very large ultimately presenting with signs of other hormone deficiency or visual disturbance due to optic chiasm compression.

28
Q

Treatment of hyperprolactaemia:

A

Dopamine agonists:
Cabergoline– is an ergot dopamine agonist that is administered once or twice a week and has much less tendency to cause nausea thanbromocriptine – usually first line
Bromocriptine – needs to be taken daily
Quinagolide – non-ergot alternative

29
Q

What is the treatment for hypercalcaemia?

A

Bisphosphonates
Calcitonin
Corticosteroids (high Vit D, sarcoidosis)

Hypercalcaemia >3.5 mmol/L = emergency

IV 0.9% sodium chloride
IV Zoledronic acid 4mg over 15 min (once fully rehydrated)

30
Q

What are bisphosphonates?

A

Pyrophosphate analogues that bind to hydroxyapatite crystals in the bone matrix
Inhibit osteoclast resorptive action on bone
Bisphosphonates are poorly absorbed from the gut
Orally best taken once weekly on an empty stomach to avoid binding by Ca2+in food
Care with swallowing – take with large glass of water and stay upright for 30 min – oesophageal injury reported

Side effects: necrosis or jaw, fractures

31
Q

Why is it important to correct magnesium in calcium disturbances

A

Need magnesium for PTH to work properly. So low magnesium makes correcting calcium levels very hard

32
Q

What is the management for Addison’s?

A

Glucocorticoid and mineralocorticoid replacement therapy
Patient education
MedicAlert bracelet

33
Q

Management of steroid dose in an Addison’s patient if their is an illness:

A

Double glucocorticoid (hydrocortisone)

Can keep fludrocortisone dose the same

34
Q

What is seen in MEN Type 1:

A

(3 P’s)
Hyperparathyroidism
Pituitary tumour
Pancreas tumour: insulinoma, gastrinoma

Most common presentation is Hypercalcaemia

35
Q

What is seen in MEN Type IIa

A

Medullary thyroid cancer

(2 P’s)
Parathyroid
Phaechromocytoma

RET Oncogene

36
Q

What is seen in MEN Type IIa

A

Medullary thyroid cancer

(1 P)
Phaechromocytoma - Marfoid body habitus, neuromas

RET Oncogene

37
Q

What is the test for diabetic nephropathy is the annual diabetic review?

A

ACR in early morning specimen

38
Q

What is Subacute thyroiditis? What are the 4 phases?

A

De Quervain’s thyroiditis and subacute granulomatous thyroiditis - is thought to occur following viral infection and typically presents with hyperthyroidism.

P1 - Hyperthyroidism, painful goitre, raised ESR
P2 - Euthyroid
P3 - Hypothyroidism
P4 - euthyroid

39
Q

What is sick euthyroid syndrome?

A

Changes to TFTs is reversible upon recovery from the systemic illness and hence no treatment is usually needed.

40
Q

How does myxoedema coma present?

A 
Altered mental state 
Hypothermia
Sparse hair, cool dry skin 
Bradycardia
Non-pitting oedema 
Facial swelling
41
Q

What can precipitate a myxoedema coma?

A

Infections
Medications - amiodarone, beta blockers, surgery
Trauma
Stroke

Met (7 decks)

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