Hyperthyroidism

Question 1

What is it + what is thyrotoxicosis

Answer 1

• Overactivity of thyroid gland

- THYROTOXICOSIS =condition occuring due to excessive thyroid hormone (incl hyperthyroidism)

Question 2

How common is it

Answer 2

1 in 2,000 annually

Question 3

Who does it affect

Answer 3

Grave’s = adults 2% women + 0.2% men

Question 4

What are the causes

Answer 4

GRAVES - most common cause

• autoimmune basis (med by Abs which stim TSH receptor)
• -> ++ secretion T4/3 and hyperplasia thyroid follicular cells –> goitre
• HLA region, CTLA4 + PTPN22 linked –> code for immune proteins

Question 5

What are the risk factors

Answer 5

FHx
High iodine intake
Smoking
Trauma (incl surgery)
Childbirth
HAART (highly active antiretroviral therapy)

Question 6

What is the pathophysiology of hyperthyroidism

Answer 6

• 1o = pathology within gland.
• 2o = thyroid gland stimulated by ++ thyroid-stimulating hormone (TSH) in the circulation
• Thyroid stim/ controlled by TSH (from ant. pituitary)
• TSH rel by TRH from hypothalamus
• Thyroid prod T4 + T3 (T4 need to be converted to T3 –> happens in liver/ kidney)
• Only free thyroid hormone = active (most is bound to proteins – thyroglobulin)
• Free thyroid hormones act –ve on hypothalamus + pituitary = decrease release TRH + TSH

Question 7

What are the symptoms of hyperthyroidism

Answer 7

• Weight loss despite appetite
• (May experience decrease appetite)
• Irritability/ nervousness – mental illness (anxiety)
• Weakness/ fatigue
• Diarrhoea (frequent bowel movement)
• Sweating
• Tremor
• Thinning of hair
• Heat intolerance
• Loss of libido
• Oligomenorrhoea or amenorrhoea

Question 8

What are the signs of hyperthyroidism

Answer 8

• Palmar erythema ( + Sweaty + warm palms)
• Proximal myopathy (muscle weakness +/- wasting)
• Fine tremor
• Tachycardia
• Goitre
• Brisk reflex
• Gynaecomastia
• Lid lag

Question 9

What are some differential diagnoses

Answer 9

Phaechromocytoma

Any causes weight loss

Question 10

What are some other causes of thyrotoxicosis other than GRAVES

Answer 10

• Toxic nodular goitre – multinodular goitre w/out symptoms of Graves
• Solitary thyroid nodule – palpable, toxic adenoma
• De Quervain’s thyroiditis – Transient hyperthyroidism from VIRAL – features of hyperthyroidism w/ fever + pain in neck
• Self-medication/ Drugs – over counter iodine or amiodarone, lithium
• Follicular carcinoma of thyroid gland
• Ovarian teratomas

Question 11

What investigations would you perform

Answer 11

TFTs- serum TSH can exclude 1o thyrotoxicosis, confirm w/ free T4 levels

• If TSH suppressed but free T4 normal need to look for T3
• Decreased TSH but with increased T4/3
• Decreased and normal T4/3 – could be subclinical hyperthryoidism

Autoantibodies – Most commonly seen in graves

• Antimicrosomal Abs – against thyroid peroxidase – present in 75% Graves (distinguish from toxic nodular hyperthryroidism)
• TSH-receptor Abs – present in Graves

Imaging – Thyroid USS, thyroid uptake scan (hot = overactivity, cold = not activity)

Inflammatory markers – in subacute thyroiditis CRP + ESR often raised

Question 12

How do you treat hyperthyroidism

Answer 12

• Beta-blockers used for rapid symptom control - whilst waiting for thyroid function to normalise
• Anti-thyroid drugs
• Radio-iodine
• Surgery

Question 13

What are the details of anti-thyroid drugs + SEs

Answer 13

• Carbimazole (methimazole) or propylthiouracil (thioamides – only used in thyroid storm/ pregnancy since causes liver failure)
- Inhibit prod thyroid hormones – full benefit after 2-3 weeks
- Either ‘block + replace’ = anti-thyroid drug given w/ thyroxine replacement
- Or ‘dose titration’ – only anti-thyroid drugs used + dosages adjusted to achieved normalization
- Once euthryoid –> dose reduced till pt on lowest necessary amount
• SE = nausea + bitter taste, warn pt to come for FBC if sore throat (can cause bone marrow suppression)

Question 14

What are the details of radiotherapy treatment

Answer 14

• Radioactive iodine given to pt to drink – taken up by thyroid gland = DESTRUCTION (3-4 months to take effect)
• Cheaper, need to stop anti-thyroid drugs, cannot be given to pregnant/breast-feeding females
• May worsen eye disease + cause hypothyroidism

Question 15

What are the details of surgical treatment

Answer 15

• Used infrequently – need to be returned to euthryoid state to avoid thyroid storm
• Used if suboptimal response to medication/ radio-iodine (esp pregnant or have Graves orbitopathy)
• Toxic adenoma/ toxic multinodular goitre which = resitant to conservative Tx surgical
• Complications – haemorrhage, hypothyroidism, vocal cord paralysis
• May develop hypothyroidism