Endo - Hyper & Hypothyroidism

Question 1

What is the function of TSH?

Answer 1

• Activates the uptake of iodine into the thyroid gland
• Activates proteolytic enzymes in the thyroid gland which breaks down proteins to allow for the release of thyroxine into the bloodstream

Question 2

How is thyroxine produced?

Answer 2

Iodine is absorbed into the throid gland which coverts mono-iodo-tyrosine and di-iodio-tyrosine into tri-iodo-tyrosine and thyroxine

Question 3

What is the hypo pituitary thyroid axis?

Answer 3

1) TRH in the hypothalamus goes to the pituitary gland
2) TRH in the pituitary gland causes TSH release to the thyroid gland
3) The thyroid gland produces T3 & T4 which has negative feedback on the hypothalamus and pituitary gland

Question 4

What is Grave’s disease?

Answer 4

• Autoimmune disease of the thyroid gland where antibodies bind to TSH receptors in the thyroid and cause hyperthyroidism and goitre (smooth thyroid)
• Different antibody binds to growth factor hormone in eye and causes exophthalmos
• Other antibodies cause pretibial myxoedema (hypertrophy)

Question 5

How can you detect the thyroid on a medical scan?

Answer 5

Give the patient radio-iodine and it will only be taken up by the thyroid

Question 6

What is Plummer’s disease?

Answer 6

A benign adenoma that is overactive at making thyroxine
Toxic nodular goitre (not smooth)
Not autoimmune

Question 7

What are the effects of thyroxine on the sympathetic nervous system?

Answer 7

Sensitises beta adrenoceptors, so with normal adrenaline levels, higher response which can result in tachycardia, palpatations, tremor in hands, lid lag

Question 8

What is thyroid storm?

Answer 8

If a patient has sudden hyperthyroidism, there a very high levels of thyroxine which can cause:
- Hyperpyrexia
- Accelerated tachycardia
- Cardiac failure
- Delirium/frank psychosis
- Hepatocellular dysfunction; jaundice
50% MORTALITY RATE

Question 9

How can you treat thyroid storm?

Answer 9

• Thyroidectomy
• Radioiodine
• Drugs

Question 10

What classes of drugs can be used for hyperthyroidism and how do they work?

Answer 10

1) Thionamides
2) Potassium iodide
3) Radioiodine
4) Beta-blockers
1,2&3 - Reduce thyroid hormone synthesis
4 - Block oversensitive receptors, reduces symptoms

Question 11

What are the side effects of thionamides?

Answer 11

Agranulocytosis - usually reduction in neutrophils - rare and reversible on withdrawal of the drug
Rashes - relatively common

Question 12

What are the complications associated with thyroid surgery?

Answer 12

• Risk of voice change
• Risk of losing parathyroid glands
• Scarring
• Anaesthetic

Question 13

What are the symptoms of viral thyroiditis?

Answer 13

• Painful dysphagia
• Hyperthyroidism
• Pyrexia (raised temperature)
• Thyroid inflammation

Question 14

What occurs in viral thyroiditis?

Answer 14

• All stored thyroxine is released as the virus particles replicate and cause lysis of the thyroid follicle cells
• Free T4 levels rise
• TSH levels drop
• 1 month hyperthyroidism
• No new thyroxine is being produced as the virus cells stopped production of this
• This leads to hypothyroidism

Question 15

What is hashimoto’s disease?

Answer 15

Autoimmune destruction of the thyroid gland resulting in hypothyroidism