Thyroid Disease Flashcards
Describe the physiology of the thyroid: formation of thyroxine [9]
- I- absorbed through Na/I symporter into thyroid follicular cell (basolateral side)
- I- diffuses to apical side
- On apical surface, it goes through pendrin
- Now the I- is in the follicle colloid
- It gets oxidised by TpO (thyroid peroxidase) from I- → I0
- Tyrosine + I0 link to form either MIT or DIT (mono- or diiodotyrosine)
- MIT + DIT = T3; DIT + DIT = T4
- Endocytosis: lysosomal enzymes breakdown thyroglobulin → releasing T3 & T4 into cytoplasm
- Most the T3 and T4 are bound to thyroid-binding globulin, some to transthyretin or albumin
Describe the regulation of thyroid system [7]
- Hypothalamus releases thyrotropin-released hormone (TRH)
- TRH stimulates the anterior pituitary gland, which releases thyroid stimulating hormone (TSH)
- TSH stimulates the thyroid gland which then releases thyroid hormones T3 and T4
- T3 acts as a nuclear receptor
- Thyroid hormones have several effects on the body:
- Increased metabolism
- Stimulates growth and development
- Increased catecholamine effect
List the signs [5] and symptoms [6] of hyperthyroidism
- Symptoms:
- Tiredness
- Weight loss
- Diarrhoea
- Heat intolerance
- Tremor
- Oligomenorrhoea (irregular periods)
- Signs:
- Fast pulse
- Visible (fine) tremor
- Gritty sore eyes
- Thin hair
- Palmar erythema
What are the causes of hyperthyroidism? [6]
- Graves’ Disease - primary thyrotoxicosis
- Toxic Multinodular Goitre - primary thyrotoxicosis
- Toxic Adenoma - primary thyrotoxicosis
- Ectopic Thyroid Tissue
- Pituitary Adenoma
- Exogenous Causes
State the risk factors [3], triggers [3] and conditions associated [3] with Grave’s disease
- Risk factors:
- Genetic susceptibility (HLA, TG, thyroid receptor)
- Environmental (iodine, tobacco smoke)
- Immune modulating treatment (interferon, alemtuzumab [anti-CD52 monoclonal antibody])
- Triggers:
- Stress
- Infection
- Childbirth
- Associated conditions: (→ autoimmune)
- Vitiligo
- Type 1 DM
- Addison’s
Who typically gets toxic multinodular goitre? [2]
- Elderly
- People in iodine deficient areas
What investigations should you carry out on a patient with suspected hyperthyroidism and what results would you expect to get? [9]
- Thyroid Function Tests (TFTs)
- Suppressed TSH
- Decreased T4
- Increased T3
- In Graves’, there may be…
- Mild normocytic anaemia
- Mild neutropenia
- Thyroid antibodies:
- TSH receptor antibodies
- Thyroid peroxisomal antibody (TPO)
- 123Iodine uptake scan
What are the treatment options for hyperthyroidism? [4]
- Drugs:
- Β-blockers (e.g. propranolol)
- Anti-thyroid medication:
- Carbimazole 40mg daily (propylthiouracil)
- 131I (radioactive iodine)
- Surgery - total thyroidectomy
List the signs and symptoms of thyroid eye disease [8]
- Eye discomfort
- Grittiness
- Increased tear production
- Photophobia
- Exophthalmos - appearance of protruding eye
- Proptosis - eyes protrude beyond the orbit
- Conjunctival oedema
- Papilloedema
How do you treat thyroid eye disease? [3]
- Treat hyper or hypothyroidism
- Advise to stop smoking
- Treat symptomatically
List the signs [5] and symptoms [7] of hypothyroidism
- Symptoms:
- Tiredness
- Decreased mood
- Cold intolerance
- Weight gain
- Constipation
- Menorrhagia
- Hoarse voice
- Signs:
- Bradycardia
- Reflexes relax slowly
- Cerebellar ataxia
- Dry thin hair/skin
- Moderate goitre
What are the causes of hypothyroidism? [5]
- Hypopituitarism
- Thyroidectomy
- Post-radioactive iodine ablation
- Hashimoto’s thyroiditis
- Blocks TSH receptor antibodies
- Inborn errors
- Congenital hypothyroidism/cretinism
What is the typical clinical presentation of congenital hypothyroidism/cretinism? [9]
- Coarse facial features
- Macroglossia
- Large fontanelles
- Umbilical hernia
- Mottled, cool, and dry skin
- Developmental delay
- Pallor
- Myxoedema
- Goitre
What values do you expect in thyroid function tests (TFTs) in a patient with hypothyroidism? [2]
- Increased TSH
- Decreased T4
What drugs are used to treat hypothyroidism? [2]
- Levothyroxine
- Amiodarone
