1. Thyroid Disease
Dr J. Bennett FY2

2. Objectives To understand basic thyroid axis physiology
To know the common causes of hypo and hyperthyroidism
To recognise the signs and symptoms associated with hypo and hyperthyroidism
To understand TFT interpretation
To know the management for hypo and hyperthyroidism, and the more important complications associated with these

3. Hypothalamus-Pituitary-Thyroid Axis
Hypothalamus secretes thyrotropin-releasing hormone (TRH)
TRH stimulates thyroid stimulating hormone (TSH) from anterior pituitary.
TSH stimulates T3 & T4 production from the thyroid
T3 & T4 exert –ve feedback on the pituitary and hypothalamus.

4. Hypothyroidism - Aetiology
Primary hypothyroidism
Autoimmune mediated
Primary atrophic hypothyroidism
Hashimoto’s thyroiditis
Acquired
Iatrogenic – Post-thyroidectomy or radio-iodine treatment
Drug-induced – Anti-thyroid, lithium, amiodarone
Iodine deficiency – Most common cause worldwide
Sub-acute thyroiditis – May result in thyroroxicosis for first 4-6 weeks
Post partum thyroiditis
Sick euthyroidism -
Secondary hypothyroidism – hypopituitarism (rare)

5. Hypothyroidism – Signs and Symptoms
Weight gain
Fatigue, lethargy
Dislike of cold
Constipation
Menorrhagia
Hoarse voice
Myalgia
Carpal tunnel syndrome
Psychiatric symptoms
Depression
Dementia
Signs
General
Dry skin and hair
Goitre
Non-pitting oedema
Facial features – purple lips, malar flush, periorbital oedema, lateral eyebrow loss
CVS
Bradycardia
Neuro
Cerebellar ataxia
Slow relaxing reflexes
Peripheral neuropathy

6. Hyperthyroidism – Aetiology
Hyperthyroidism (thyrotoxicosis)
Graves Disease (76%)
IgG antibodies directed against TSH receptors on thyroid – stimulates T3 & T4 production and proliferation of thyroid follicular cells
Long term can result in hypothyroidism
Toxic adenoma and toxic multinodular goitre
Autonomously secretes thyroid hormones, inhibits endogenous TSH
Thyroiditis
Iodide induced
TSH induced – eg TSH secreting pituitary adenoma (rare)

7. Hyperthyroidism – Signs and Symptoms
Weight loss
Increased appetite
Heat intolerance
Palpitations
Fatigue
Sweating
Diarrhoea
Oligomenorrhoea
Psychiatric symptoms
Irritability
Emotional lability
Psychosis
Signs
General
Hair thinning
Goitre
Lid lag, lid retraction
Pre-tibial myxoedema
Eye signs
Palmar erythema
CVS
Tachycardia AF
Neuro
Fine tremor

8. Hyperthyroidism – Eye Disease
Associated with Graves’ disease
Inflammation of retro-orbital tissues
Symptoms
Eye discomfort, grittiness
Excess tear production
Photophobia
Diplopia
Decreased acuity
Signs
Exopthalmos
Proptosis
Opthalmoplegia

9. Investigations – TFTs T3, T4 + TSH TSH + T3, T4 Hypothyroidism-
TSH
TSH
TSH + -
T3, T4
T3, T4
T3, T4
Hypothyroidism
Hyperthyroidism
Hypopituitarism
TSH secreting tumour
↑TSH; ↓T4,T3
↓TSH; ↑T4,T3
↓TSH; ↓T4,T3
↑TSH; ↑T4,T3

10. Investigations – Other tests
Bloods
Thyroid auto-antibodies
TSH receptor antibodies – Graves’ disease
USS Thyroid + FNAC
Isotope scan

11. Hypothyroidism - Management
Conservative
Lifestyle - smoking cessation, weight loss
Medical
Levothyroxine (T4) – adjust dose according to clinical response and normalisation of TSH levels. Caution required in patients with IHD as exacerbation of myocardial ischaemia and infarction are known complications
Surgical
Symptomatic – carpal tunnel decompression, thyroidectomy if compression of local structures

12. Hyperthyroidism - Management
Conservative
Smoking cessation – especially with Graves’s ophthalmology, associated with worse prognosis
Medical
Symptomatic – β-blockers
Carbimazole, propylthiouracil
Risk of agranulocytosis
Radio-iodine treatment – caution in patients of childbearing age; must avoid contact with pregnant women and small children
Long term likely to become hypothyroid
Usually avoided in Graves’ disease

13. Hyperthyroidism - Management
Surgical
Subtotal/total thyroidectomy
Orbital decompression if thyroid eye disease causing compression of optic nerve
Complications of thyroid surgery
Immediate
Haemorrhage (haematoma can cause airway obstruction)
Short term
Infection
Long term
Damage to laryngeal nerve – hoarse voice
Hypothryoidism
Transient hypocalcaemia
Hypoparathyroidism

14. Thyroid Storm
Medical emergency (rare) – 10% mortality even with early recognition and management
Aetiology -
Infection in a patient with unrecognised or inadequately treated thyrotoxicosis
Post 131I treatment or post sub-total thyroidectomy
Signs
Fever
Agitation and confusion
Tachycardia +/- AF
Management
IV fluids
Broad spectrum antibiotics
Propanolol, digoxin
Antithyroid drugs – sodium ipodate, Lugol’s solution, carbimozole

15. Thyroid Cancers Type of tumour Frequency (%)
Age at presentation (years)
20 year survival (%)
Papillary 70
20-40 95
Follicular 10
40-60 60
Anaplastic 5
>60
<1
Medullary
5-10
>40 50
Lymphoma

16. Clinical Scenario
39 year old lady presents with 3 months history of weight loss and diarrhoea.
She has been suffering from excessive sweating and a recent family holiday to Tunisia was ruined as she was unable to tolerate the weather. Her eyes also feel gritty a lot of the time and she has had friends ask her why she is staring at them. She is otherwise well and her only medication is St John’s Wort. She has no known allergies. She does not smoke and drinks alcohol socially. On exam she is slight with sweaty palms and a fine tremor when her arms are out stretched. Her pulse is 100bpm and irregularly irregular. She has exophthalmos and lid lag. She also has a diffuse non tender swelling on the front of her neck which moves with swallowing.
What are your differentials for this lady?
How would you investigate her?
How would you manage her?
What are the cardinal features of Grave’s disease?
What drug is used in pregnant hyperthyroid patients?
What are complications of thyroid surgery?

17. Further topics to cover
Thyroid Anatomy
Cellular structure and function
Blood supply
Thyroid physiology
Production of T3 and T4 in thyroid follicles
Transport of T3 and T4 (protein binding)
Peripheral conversion of T4 to T3
Further TFT results and their significance
Impact of amiodarone on the thyroid – complex, can cause both hypo and hyperthyrodism
Details of thyroid malignancy
Management of thyroid disease in pregnancy