Endocrine Pathology - The Thyroid Gland Flashcards
Tests to be performed when hyperthyroidism is suspected.
- T3
- T4
- TSH
All will have ↓TSH (except the rare TSH-secreting pituitary adenoma). Most have ↑T4 but around 1% have only raised T3.
Tests to be performes when hypothyroidism suspected or monitoring replacement
- T4
- TSH
T3 does not add any extra information. Perfrom TSH at same time when monitoring as it vaires throughout the day. (Trough at 2pm, 30% higher in the evenings.
Sick euthyroidism
In any systemic illness, TFTs may become derranged. The typical pattern is for everything to be low. The test should be repeated after recovery.
Diagnosis for ↑TSH, ↓T4
Hypothryroidism
Diagnosis for ↑TSH, normal T4
Treated hypothyroidism or subclinical hypothyroidism
Diagnosis for ↑TSH, ↑T4
TSH secreting tumour or thyroid hormone resistance
Diagnosis for ↑TSH, ↑T4, ↓T3
Slow conversion of T4 to T3 or thyroid hormone antibody artefact
Diagnosis for ↓TSH, normal ↑T4 T3
Subclinical hyperthyroidism
↓TSH, ↓T4
Central hypothyroidism (hypothalamic or pituitary disorder)
↓TSH, ↓T4 and ↓T3
Sick euthyroidism or pituitary disease
Normal TSH, abnormal T4
Consider changes in thyroid binding globulin, assay interference, amiodarone, or pituitary TSH tumour.
Other tests for thyroid disease
- Thyroid autoantibodies - increased in Hashimoto’s or Grave’s disease
- TSH receptor antibody - may be increased in Grave’s disease
- Serum thyroglobulin - useful in monitoring the treatment of carcinoma and in detection of factitious (self-medicated) hyperthyroidism where it is low
- Ultrasound - distinguishes cystic (usually benign) from solid (possibly malignant) nodules
- If solitary large nodule do a fine needle aspiration for thyroid cancer
- Isotope scan
Screen the follwing for abnormalities in thyroid function
- Patients with atrial fibrillation
- Patients with hyperlipidaemia
- Diabetes mellitus - on annual review
- Patients on amiodorone or lithium (6 monthly)
- Patients with Down’s or Turner’s syndrome, or Addison’s disease (yearly)
Symptoms of thyrotoxicosis
- diarrhoea
- ↓weight
- ↑appetite
- over-active
- heat intolerance
- palpitations
- tremor
- irritability
- oligomenorrhoea +/- infertility
Signs of thyrotoxicosis
- pulse fast/irregular
- warm moist skin
- fine tremor
- palmar erythema
- thin hair
- lid lag
- lid retraction
- goitre, thyroid nodule or bruit depending on the cause
Signs of Grave’s disease
- Thyroid eye disease - exophthalmos, opthalmoplegia
- Pretibial myxoedema (oedematous swellings above lateral malleoli)
- Thyroid acropachy (extreme manifestations with clubbing, painful finger and toe swelling, and periosteal reaction in limb bones
Causes of thyroitoxicosis
- Grave’s disease
- Toxic multinodular goitre
- Toxic adenoma
- Etopic thyroid tissue
- Exogenous - iodine excess
Treatment of thyrotoxicosis
- Pharmacological
- Beta blockers - for rapid control of symptoms
- Carbimazole
- Radioiodine
- Thyroidectomy
Complications of thyrotoxicosis
- Heart failure
- Angina
- AF
- Osteoporosis
- Opthalmopathy
- Gynaecomastia
- Thyroid storm
Symtoms of thyroid eye disease
- eye discomfort
- grittiness
- ↑tear production
- photophobia
- diplopia
- ↓acuity
- afferent pupillary defect - may indicate optic nerve compression
Signs of thyroid eye disease
- Exophthalmos (appearance of the protruding eye)
- Proptosis (eyes protrude beyond the orbit - look from above in the same plane as the forehead)
- Loss of colour vision
- Opthalmoplegia
Symptoms of hypothyroidism
- constipation
- ↑weight
- lethargic/tired
- cold intolerance
- hoarse voice
- ↓mood
- ↓memory and cognition
- menorrhagia
Signs of hypothyroidism
BRADYCARDIC
- Bradycardic
- Reflexes relax slowly
- Ataxia (cerebellar)
- Dry thin hair / skin
- Yawning / drowsy
- Cold hands / ↓temperature
- Ascites +/- non-piting oedema +/- pericardial/pleural effusion
- Round puffy face / obese
- Defeated demenour
- Immobile +/- ileus
- Congestive cardiac failure
Also: nephropathy, myopathy, goitre
Primary causes of hypothyroidism
- Primary atrophic hypothyroidism
- Hashimoto’s thyroiditis
- Iodine deficiency (chief cause worldwide)
- Post thyroidectomy or radioiodine treatment
- Drug induced - antithyroid drugs, amiodarone, lithium, iodine
- Subacute thyroiditis
Causes of secondary hypothyroidism
Not enough TSH due to hypopituitarism - very rare
Treatment of hypothyroidism
Levothyroxin
