Thyroid Flashcards
TSH ↑
T4 ↓
Hypothyroidism
TSH ↑
T4 -
Subclinical hypothyroidism
TSH ↑
T4 ↑
TSH-secreting tumour
OR
Thyroid hormone resistance
TSH ↓
T4 ↑
T3 ↑
Hyperthyroidism
TSH ↓
T4 -
T3 -
Subclinical hyperthyroidism
TSH ↓
T4 ↓
T3 ↓
Central hypothyroidism (hypothalamic or pituitary cause)
Thyroid-stimulating hormone is sometimes known as…
Thyrotropin
Which structure produces TSH?
The anterior pituitary gland
How is T3 produced?
- 85% is formed from peripheral conversion of T4
- 15% is produced directly by the thyroid gland
How do thyroid hormones travel in the plasma?
Thyroid hormones are mainly protein bound, e.g. to thyroxine-binding globulin (TBG)
Which is more useful: free T3 and T4; or total T3 and T4? Why?
- free T3 and T4 is more useful
- total T3 and T4 rises and falls in line with TBG levels
What affects TBG levels?
Increase TBG: - pregnancy - oestrogen therapy - hepatitis Decrease TBG: - nephrotic syndrome - malnutrition - drugs (androgens, corticosteroids, phenytoin) - chronic liver disease - acromegaly
What antibody is commonly screened for when autoimmune thyroid disease is suspected?
Antithyroid peroxidase (TPO)
Which groups of patients should be screened for abnormalities in thyroid function?
Patients with: - AF - hyperlipidaemia - diabetes - Down's syndrome - Turner's syndrome - Addison's disease - Gestational diabetes Patients treated with: - Amiodarone - Lithium
Symptoms of hypothyroidism
- tiredness
- cold intolerance
- constipation
- depression
- bradykinesia
- slow thoughts, depression and memory problems
- muscle aches, weakness or cramps
- decreased libido
- carpal tunnel syndrome
- irregular or heavy periods
Symptoms of hyperthyroidism
- irritability and anxiety
- hyperactivity
- labile emotions
- insomnia
- feeling tired all the time
- heat intolerance
- palpitations
- muscle weakness
- polyuria
- polydipsia
- diarrhoea
- pruritus
- oligomenorrhoea (+/- infertility)
- loss of interest in sex
Signs of hyperthyroidism
- goitre
- arrhythmia (AF or SVT, VT is rare)
- tachycardia
- fine tremor
- warm, moist skin
- palmar erythema
- urticaria
- hair loss or thinning
- weight loss (often despite and increased appetite)
- lid lag
- eye redness and dryness
- exophthalmos
- ophthalmoplegia
- pretibial myxoedema
Causes of hyperthyroidism
- graves disease
- toxic multinodular goitre
- toxic adenoma
- ectopic thyroid tissue
- exogenous
- subacute de Quervain’s thyroiditis
- drugs e.g. amiodarone
- postpartum
- TB (rare)
What is the ratio of men and women affected by Grave’s disease?
- 9:1
- more women than men
What age group is typically affected by Grave’s disease?
40-60 years old
What are the potential complications of thyrotoxicosis?
- heart failure
- angina
- AF
- osteoporosis
- ophthalmopathy
- gynaecomastia
- thyroid storm
Signs of hypothyroidism
- dry and scaly skin
- weight gain
- pallor
- brittle hair and nails
- reflexes relax slowly
- cerebellar ataxia
- cold hands
- ascites
Causes of primary hypothyroidism
- primary atrophic hypothyroidism
- Hashimoto’s thyroiditis
- iodine deficiency
- thyroidectomy
- radioiodine treatment
- drug induced
What is secondary hypothyroidism?
- not enough TSH due to hypopituitarism
- very rare
