Hypo- / Hyperthyroidism

Question 1

Function of thyroid

Answer 1

synthesis of thyroid hormones, T3 and T4 (thyroxine)

secretes calcitonin

Question 2

Function of parathyroid

Answer 2

maintenance of serum calcium and phosphate levels through secretion of parathyroid hormone (PTH)

Question 3

Anatomy of thyroid

Answer 3

Found in neck - butterfly shape

Made up of: superior parathyroid and inferior parathyroid glands

Question 4

mechanism of thyroid hormone production

Answer 4

1. hypothalamus releases thyroid-releasing hormones (TRH)
2. TRH stimulates pituitary gland to produce thyroid-stimulating hormone (TSH)
3. TSH stimulates thyroid to produce T3 and T4
   - increased T3/T4 conc inhibits TRH = negative feedback loop

Question 5

Examples of hyperthyroid diseases

Answer 5

Thyroiditis 
Primary hyperthyroidism:
- Graves disease 
- Toxic multinodular goitre 
- Toxic adenoma 
Nodular disease
Pituitary disease

Question 6

Thyroiditis

Answer 6

= inflammation of thyroid follicles that can lead to irreversible damage and hypothyroidism - causes ‘leakage’ of T3/T4

caused by: infection, trauma, drug-induced, autoimmune mediated

Question 7

Symptoms of Hyperthyroidism

Answer 7

MH issues 
insomnia 
bulging eyes 
weight loss
diarrhoea 
N + V 
muscle weakness 
irregular menstruation

Question 8

Treatment options for hyperthyroidism

Answer 8

anti-thyroid drugs (thionamides)
thyroidectomy
radioactive iodine - slowly destroys cells of thyroid that produce thyroid hormone

Question 9

Primary hypothyroidism

Answer 9

= dysfunction of thyroid itself

most prominent

Question 10

Secondary hypothyroidism

Answer 10

= reduced thyroid stimulation

pituitary-hypothalamic dysfunction

Question 11

symptoms of hypothyroidism

Answer 11

hair thinning 
jaundice 
HTN 
MH issues 
heart attack risk 
decreased metabolism 
stomach bloating 
weakness 
dry skin 
constipation 
menstrual changes

Question 12

Thyroid function tests and results

Answer 12

Secondary hyperthyroidism (rare) - hi TSH and hi T4
Subclinical hypothyroidism - hi TSH and normal T4
Primary hypothyroidism - hi TSH and low T4
Primary hyperthyroidism - lo TSH and hi T4
Subclinical hyperthyroidism - low TSH and normal T4
Secondary hypothyroidism (rare) - low TSH and low T4

Question 13

Treatment options for hypothyroidism

Answer 13

1st line - levothyroxine

alternative - liothyronine IV (not recommended)

Question 14

Aims of hypothyroidism treatment

Answer 14

replace thyroid hormone

correct TSH levels and resolve clinical symptoms

Question 15

Thyroid crisis (thyrotoxic storm)

Answer 15

overproduction of thyroid hormones = extreme hyperthyroidism

Question 16

Causes and symptoms of thyroid crisis

Answer 16

Causes:

• TSH secreting pituitary adenoma
• pituitary resistance to thyroid hormone
• trauma
• meds
• over-treatment with levothyroxine

Symptoms

• hyperthermia
• confusion
• jaundice
• N+V
• tachycardia
• dehydration
• hypotension

Question 17

4 aspects of treatment for thyroid crisis

Answer 17

1. inhibit hormone synthesis
   - carbimazole or propylthiouracil
2. inhibit thyroid hormone release
   - iodine
3. inhibit peripheral action of excess thyroid hormone
   - glucocorticoids (inhibit T4 to T3 conversion)
   - propanolol (control HR)
4. supplementary management
   - paracetamol (lower temp)
   - cholestyramine (binds to thyroxine and excretes it)