Thyroid (easy peasy!)

Dr Lucie Spooner- F1

The plan.... 1. Anatomy- zzzzz2. HPA Axis3. Hypothyroidism4. Thyrotoxicosis5. Carbimazole- what you need to

know6. Surgical complications7. Thyroid and pregnancy8. Cases x4.

Pituitary Gland- just learn these. Anterior:FSHLHProlactinGHACTHTSH

Posterior:ADHOxytocin

Definitions• Hypothyroidism:

– clinic state from decreased production of and/or effect of thyroid hormones

• Hyperthyroidism: – clinical state of increased circulation of

free thyroid hormones. Excessive Thyroxine (T3 or T4 or both).

Hypothyroidism- clinical features• Weight gain• Cold intolerance• Hair loss and Dry skin• Bradycardia

– Pericardial effusion– Premature IHD

• Constipation• Menstrual Disturbances

– Menorrhagia (Anaemia)– Amenorrhoea (Rare)

• Mentally Slow– Depression– Psychosis– Cerebellar disturbances

• Facial puffiness• Bilateral Carpal Tunnel Syndrome• Slow relaxing reflexes• Hair loss

Hypothyroidism- CausesCaused by thyroid (primary) the pituitary

(secondary) or the hypothalamus (tertiary).

PRIMARY: Autoimmune

- There are 3 main examples- what are they?

Primary: Acquired

- There are 3 main causes- what are they?

Primary Autoimmune1. Hashimoto's thyroiditis:

- autoimmune, very common, familial. - Autoantibody to thyroglobulin and thyroid= goitre. - Family members may have Addison's, pernicious anaemia or diabetes. - It is 10 times more common in women- anti-thyroid peroxidase and also anti-Tg antibodies

2. Atrophic hypothyroidism: - autoimmune, elderly, autoantibody to TSH receptor. - No goitre.

3. Congenital Hypothyroidism: -should be picked up in first 4 weeks or high risk of mental retardation- screened neonatally.

Primary- Acquired:1. Iodine deficiency (Endemic goitre). 2. Iodine excess (Amiodarone).3. Post treatment for Hyperthyroidism.

– Surgery– Radioiodine– Antithyroid Drugs (such as???)

Hypothyroidism- CausesSecondary• Pituitary failure= Low levels of TSH• Very rare- just mention it.

Hypothyroid- InvestigationsInvestigations:

How are they split up?

BedsideBloods RadiologySpecial Tests

Bedside- 1. ECG:• a prolonged Q-T interval• low P, T and QRS amplitude• atrioventricular and intraventricular conduction

disturbances e.g. right bundle branch block • 2. BM

Bloods• FBC shows macroscopic anaemia (MCV 95-

110). - If Hb <100 suspect an additional

cause. Can have pernicious anaemia (MCV>115) or iron deficiency anaemia from menorrhagia

• TFT: Low T4 and high TSH- primary. • Low or normal TSH- secondary or

tertiary.• Cortisol: exclude Addison's• Thyroid antibodies

Investigations- • Who would you screen ?

– Perimenopausal women and those with non specific symptoms

– Confusion– T1DM (especially those attempting to

conceive)

Management• Conservative: lifestyle- weight loss, exercise

(only subclinical!)– If subclinical- check antibodies- if negative and

asymtpomatic- screen annually. – 2% chance of clinical signs annually.

• Medical:– 50ug/day and increasing to 125-150ug/day. – Half an hour before food or won’t be absorbed. – Check free thyroxine at 6-8 week intervals– If patient remains symptomatic- what would you

do?• Surgical: see surgical lecture!

Myxoedema Coma:

Rare complication with 50% mortality rate. Suspect in any patient with hypothermia or coma. Start IV T3 (20ug bolus repeated every 6 hours). As thyroid failure may relate to pituitary disease (if Na is low), give hydrocortisone too until an accurate diagnosis is made.

Hyperthyroidism- Symptoms• Weight loss• Increased appetite• Irritability/restlessness• Palpitations• Heat intolerance• Diarrhoea• Oligomenorrhoea

Hyperthyroidism- clinical signs• Tremor• Eye complaints (Grave’s)

– Proptosis– Dry eye– Difficulty looking up– Lid lag– Opthalmoplegia

• Pretibial Myxoedema and acropachy (Grave’s)

• Atrial Fibrillation

Pretibial myxoedema• Anterior

aspect lower legs

• Indurated discoluration of the skin.

What do you see?

Thyroid Eye Disease• Occurs in Grave’s disease• Exopthalalmus • Proptosis• Opthalmoplegia• May be unilateral• May present for the first time after treatment• More common in smokers• Rarely resolves completely. • Causes: deposition of lymphocytes and oedema.

• Risk of optic nerve compression- can cause blindness, so Rx with steroids and surgery when ‘malignant exopthalmus’

Thyrotoxicosis (give me 4 causes)• Grave’s disease

– 75% cases– Thyroid-stimulating immunoglobulins (TSIs).

• Thyroglobulin.• Thyroid peroxidase• Sodium-iodide symporter.• TSH receptor.

– Goitre, eye signs and Pretibial Myxoedema• Toxic multi nodular goitre

– 15%– Older women– Likely remission after medical therapy.

• Toxic nodule/adenoma– 5%,– Likely remission after medical therapy

• De Quervains thyroiditis – Transient from acute inflammatory viral process– Accompanied fever, malaise and pain in neck

• Amiodarone induced Thyrotoxicosis• Postpartum thyroiditis• Iatrogenic - too much thyroxine• Hashimotos’s thyroiditis- .... Before you go hypo

Investigations• Bedside: • ECG, Urine dip, BM• Bloods:• Serum TSH < 0.05mU/L• Raised free T4 or T3 confirms

diagnosis• Thyroid antibodies• Radiology:• USS if lump/nodule• Special tests: • Radioisotope iodine scanning (hot

or cold nodule)• FNA for cytology (more relevant if

cancer suspected)

Thyrotoxic storm – medical emergency• Rapid deterioration of hyperthyroidism

with 10% mortality• Severe tachycardia, restlessness,

hyperpyrexia, cardiac failure• Precipitated by stress, infection or

surgery in the unprepared patient• High dose BB and start carbimzole or

propylthiouracil immediately and give iodide and hour later and IV steroids to inhibit new thyroid hormone production.

Management• Conservative:

– Lubricant eye drops such as methylcellulose– Stop smoking– Tape eye lids to ensure closure at night– Systemic steroids 30-120mg OD to reduce inflammation

if severe• Medical:

– Beta Blockers – alleviated symptoms such as tremor and palpitations, normally the first Rx initiated.

– Antithyroid drugs:• Carbimazole - inhibit formation of thyroid hormone• Propythiouracil - safe in pregnancy

– Radioactive iodine• Contraindicated in pregnancy• Patients must be euthyroid before treatment• Can lead to hypothyroidism

• Surgical:– Thyroidectomy

Carbimazole• Grave’s:

– Use for 18-24 months and then trial without medication

• Side effects:– Most common: Urticrial rash (2-4%) – Most serious: Agranulocytosis (1/300-

500)– Arthralgia– Headache – Alopecia.– Normally develop within 4 weeks of

treatment. – If fever or sore throat- stop

medication immediately. • Most patients feel better after 10 -14

days. • Takes 4-6 weeks before euthyroid.

Complications after thyroidectomy• Immediate:

– Haemorrhage– Recurrent larangeal nerve palsy

• Intermediate:– Infection

• Long-term:– Hypothyroidism– Hypoparathyroidism

Pregnancy and thyrotoxicosis• Hyperthyroidism in pregnancy• HCG is a weak stimulator of TSH

receptor

• Very important to treat• Untreated leads to miscarriage,

premature labour, low birth weight and eclampsia.

• Radioiodine is absolutely contraindicated.

Thyroid Function Test. • First line is ONLY TSH . Lab will not check T3/T4

unless the TSH is deranged. • T4 normal range is 12-20.• TSH normal range is 0.6-6.0• Hypothyroidism:

– Primary- TSH is > 6. Secondary- TSH is low to normal. – T4/T3 low.

• Hyperthyroidism– TSH is <0.05 – T3/T4 raised as a result of negative feedback (high T4

and low TSH can also be found in Exac of COPD, RA and HF, raised T3 however is always thyrotoxicosis)

Case 139 year old lady presents with 3 months history of

weight loss and diarrhoea. On further questioning you find out that 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? (make sure these include all important differentials that must be ruled out)

• 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?

Case 2 • T4 is 12. • TSH is 7

• Subclinical• ?would you treat?• Only if symptomatic or trying to

conceive- must check for autoantibodies.

Case 3• Pt admitted with fast AF• TSH is undetectable• T4 of 36

• What would you do?• Measure T3 in this case as could be

secondary to heart failure. T3 is always raised in thyrotoxicis.

• If elevated T3 – start antithyroid medication.

Case 4• 45 yo lady with palpitations, weight

loss. • TSH undetectable• T4 is 40• Which Rx would help control her

symptoms fastest?

• Beta Blocker... Then antithyroid medication.

Key Points1.Remember to ask about red flag

symptoms. 2. With a thyroid case they may hide

the glass of water- look for it. 3.Don’t forget to treat symptoms as

well as the disease- e.g. Beta blockers.

4.Talk slowly and breath... They want to pass you. I promise.

5.Practise, practise and practise....

Any Questions?