Endocrinology - Hyperthyroidism

Question 1

Suggest possible causes for hyperthyroidism

Answer 1

1. GRAVE’S DISEASE (most common) - autoimmune production of antibodies stimulating TSH R… hyperplasia of thyroid follicular cells and excess thyroid hormone production… hyperthyroidism +/- diffuse goitre.
2. TOXIC MULTINODULAR GOITRE (2nd most common)
3. TOXIC ADENOMA - benign solitary thyroid nodule causing overactivation
4. DE QUERVAIN’S THYROIDITIS - transient hyperthyroidism probably caused by viral infection. Sx: hyperthyroidism + pyrexia + neck pain.
5. Drugs, inc. AMIODARONE, LITHIUM and EXOGENOUS IODINE
6. TSH-SECRETING PITUITARY ADENOMA - 2ndary hyperthyroidism with increased T3/4 and increased TSH.
7. GERM CELL TUMOURS, e.g. ovarian teratomas which result in increased HCG - similar structure to TSH.

Question 2

what are the effects of excess thyroid hormone?

Answer 2

• increased cellular metabolic rate
• increased heat generation
• increased activation of SNS - increased CO, increased HR, increased BP

Question 3

suggest common symptoms of hyperthyroidism

Answer 3

• weight loss despite increased appetite
• diarrhoea +/- steatorrhoea
• sweating, heat intolerance
• tremor
• weakness and fatigue
• loss of libido
• mental illness: insomnia, irritability, anxiety, psychosis
• oligomenorrhoea or amenorrhoea

Question 4

suggest common signs of hyperthyroidism

Answer 4

• sweaty warm palms
• fine tremor
• tachycardia - may be AF and/or HF
• hyperreflexia
• goitre
• gynaecomastia
• lid lag
• urticaria, pruritis
• hair thinning or diffuse alopecia

Question 5

why can lid lag be a feature of hyperthyroidism ?

Answer 5

Lids controlled by levator palpebrae superioris muscle (90% skeletal muscle and 10% SM) - SM portion controlled by SNS which is overstimulated in thyrotoxicosis

Question 6

name 2 signs which are specific to Grave’s disease

Answer 6

1. exopthalmos (anterior bulging of eyes)

2. pre-tibial myxoedema

Question 7

which investigations would you perform on someone with suspected hyperthyroidism?

Answer 7

1. Bloods
   - TFTs: increased free T4, with decreased TSH in primary hyperthyroidism and increased TSH in secondary (pituitary adenoma).
   - autoantibodies: antimicrosomal antibodies against thyroid peroxidase, antithyroglobulin antibodies, TSH R antibodies
2. Imaging
   - thyroid USS
   - radioactive iodine uptake scan: diffuse increased uptake in Grave’s disease
3. ECG: ?arrythmias

Question 8

what are the 3 management options for hyperthyroidism?

Answer 8

1. Anti-thyroid drugs
   - CARBIMAZOLE - dose-titration
   - CARBIMAZOLE + LEVOTHYROXINE - ‘block and replace’
   - PROPYLTHIOURACIL - reserved for use in pregnancy and thyroid storm as can cause severe liver failure
2. Radio-iodine
   1st line in teenagers and in relapsed Grave’s disease or in toxic nodular goitre. Cannot be given to pregnant or breast-feeding females.
3. Surgical thyroidectomy
   Indicated if suboptimal response to meds or radio-iodine esp. in pregnant pts or those with Graves’ orbitopathy.

Question 9

suggest possible complications of hyperthyoidism

Answer 9

1. thyrotoxic periodic paralysis: serious complication involving muscle paralysis and hypokalaemia due to massive intracellular shift of K+
2. thyrotoxic storm: extreme manifestation of thyrotoxicosis often precipitated by surgery, infection or other acute illness
3. osteoporosis
4. thyroid eye disease

Question 10

describe the common presentation of a thyrotoxic crisis/storm

Answer 10

• hyperpyrexia (>41 degrees) and dehydration
• HR >140 bpm +/- AF, other arrhythmias and high-output HF
• nausea, vomiting, abdo. pain, diarrhoea and jaundice
• confusion, agitation, delirium, psychosis, seizures or coma

Question 11

how would you manage a pt with a thyrotoxic storm

Answer 11

1. resuscitation, inc. IV fluids
2. Beta-blockers, e.g. IV 5 mg PROPRANOLOL
3. anti-thyroid meds - CARBIMAZOLE or PROPYLTHIOURACIL to prevent formation of further thyroid hormone
4. 100 mg IV/IM HYDROCORTISONE (continue 6 hourly) to inhibit T4 to T3 conversion
5. after 4 hrs: 1 ml PO LUGOL’S SOLUTION (continue 6 hourly) to block release of pre-formed thyroid hormone