Thyroid

• If hyperthyroidism is suspected measure T3, T4 and TSH
• In hypothyroidism measure T4 and TSH

Sick euthyroidism

• In a systemic illness TFTs may become deranged. Typically everything is low. The test should be repeated after recovery

Other tests

• Thyroid autoantibodies
  • Antithyroid peroxidase antibodies and antithyroid globulin antibodies may be increased in autoimmune thyroid disease e.g. Hashimotos and Graves disease. If it is positive in Grave’s disease there is an increased risk of developing hypothyroidism at a later stage
• TSH receptor antibody
  • May be increased in Grave’s disease
• Serum thyroglobulin
  • Useful in monitoring the treatment of carcinoma and detection of factitious (self medicated) hyperthyroidism where it is low
• Ultrasound
  • Can distinguish cystic from solid nodules. A FNA can then be done
• Isotope scan
  • 123 Iodine or 99 Technetium – useful for determining the cause of hyperthyroidism. 20% of cold nodule are malignant. Hot nodules are rarely malignant

Screening thyroid function

• The following patients should be screened for abnormalities in thyroid function;
  • Patients with AF
  • Those with hyperlipidaemia
  • Those with DM
  • Women with Type I DM during 1^st trimester and post delivery
  • Patients on amiodarone or lithium
  • Patients with Down’s syndrome, Turner’s syndrome and Addisons’ disease

Thyrotoxicosis

Symptoms

• Weight loss (paradoxical weight gain in 10-30%)
• Heat intolerance, sweating
• Diarrhoea, irritability, tremor
• Emotional lability, psychosis, itch, oligomenorrhoea

Signs

• Tachycardia
• AF
• Warm peripheries
• Fine tremor
• Palmar erythema
• Hair thinning
• Lid lag
• There may be goitre, thyroid nodules or bruit depending on the cause

Signs in Grave’s disease only;

• Eye disease – exopthalmos, opthalmoplegia
  • The main risk is smoking
  • Patient may be euthyroid, hyperthyroid or hypothyroid
• Pretibial myxoedema – oedematous swelling above lateral malleoli
• Thyroid acropatchy – extreme manifestation with clubbing, painful finger and toe swelling and periosteal reaction in the limb bones

Causes;

• Grave’s disease
  • F>>M
  • Common between 30 and 50
  • Autoimmune disease characterised by stimulatory TSH receptor antibodies (which also react with orbital antigens)
  • There is diffuse thyroid enlargement
  • Patients may be hyper, hypo or euthyroid
  • It is associated with other autoimmune disease – vitiligo, DM Type I, Addison’s disease
• Toxic multinodular goitre
  • Seen in the elderly and in iodine deficient areas
• Toxic adenoma
  • Solitary ‘hot’ nodule producing T3 and T4. The rest of the gland is suppressed

Other causes of thyrotoxicosis that aren’t due to hyperthyroidism;

• Subacute de Quervain’s thyroiditis
  • A self limiting viral infection with painful goitre, fever and raised ESR
• Drugs
  • Amiodarone, lithium (hypothyroidism is commoner)
• Exogenous
  • Thyroxine intoxification causes increased T4, reduced T3 and reduced thyroglobulin
• Ectopic thyroid tissue
  • Metastatic follicular thyroid carcinoma, choriocarcinoma or struma ovarii

Treatment

• Drugs
  • Beta-blockers for rapid control of symptoms
  • Carbimazole either titration or as block and replace therapy
• Radioiodine
  • Most become hypothyroid following treatment
  • CI – pregnancy, lactation
  • Caution in active thyrotoxicosis as can cause a thyroid storm
• Thyroidectomy
  • Risk to the recurrent laryngeal nerve and parathyroids

Complication of hyperthyroidism

• Heart failure
• Angina
• AF
• Osteoporosis
• Opthalmopathy
• Gynaecomastia
• Thyroid storm

Hypothyroidism

Symptoms

• Tiredness, lethary, depression, dislike of the cold, weight gain, constipation, menorrhagia, hoarse voice, poor cognition/dementia, myalgia

Signs

• Bradycardia
• Dry skin and hair
• Non-pitting oedema (eyelids, hands and feet)
• Cerebellar ataxia
• Slow relaxing reflexes
• Peripheral neuropathy
• ‘Toad like face’
• There may be a goitre depending on the cause or signs of CCF or pericardial effusion

Causes of primary hypothyroidism

• Autoimmune
  • Primary atrophic hypothyroidism
    • F>>M, common
    • Diffuse lymphocytic infiltration of the thyroid leading to atrophy
  • Hashimoto’s thyroiditis
    • Autoimmune disease plus goitre due to lymphocytic and plasma cell infiltration
    • Commoner in older women
    • May be hypo or euthyroid, there may be a period of hyperthyroidism initially
• Acquired
  • Iodine deficiency
  • Post thyroidectomy or radioiodine treatment
  • Drug induced – antithyroid drugs, amiodarone, lithium, iodine
  • Subacute thyroiditis – temporary hypothyroidism after hyperthyroid phase

Associations;

• Turner’s syndrome
• Down’s syndrome
• CF
• Primary biliary cirrhosis
• POEMS syndrome – polyneuropathy, organomegaly, endocrinopathy, m-protein band from a plasmacytoma, skin pigmentation

Treatment

• If you and healthy give 50-100?g/24hr levothyroxine
• If elderly or with IHD give 25?g/24hr

Thyroid emergencies

Myxoedema coma

Signs and symptoms

• Patient looks hypothyroid and is >65, hypothermia, hyporeflexia, reduced glucose, bradycardia, coma and seizures

Precipitants

• Infection, MI, stroke, trauma

Examination

• Goiter
• Cyanosis
• Heart failure
• Precipitants

Treatment

• Take blood for T3, T4, TSH, FBC, U&Es, cultures, cortisol
• Take ABG
• Give high flow O2 if cyanosed, correct any hypoglycaemia
• Give T3 5-20?g IV slowly (may precipitate manifestations of undiagnosed IHD)
• Give hydrocortisone 100mg/8hr IV
• IVI saline
• If infection is suspected give antibiotics e.g. cefuroxime 1.5mg/8hr
• Treat heart failure as appropriate
• Treat hypothermia

Further treatment

• T3 5-20 ?g/4-12hr IV until sustained improvement eg after 2-3 days
• Then give thyroxine 50 ?g/24hr
• Continue hydrocortisone
• Give IV fluids as appropriate

Hyperthroid crisis (thyrotoxic storm)

Signs and symptoms

• Severe hyperthyroidism, fever, agitation, confusion, coma, tachycardia, AF, D&V, goiter, thyroid bruit, picture of acute abdomen

Precipitants

• Recent thyroid surgery or radioiodine
• Infection
• MI
• Trauma

Diagnosis

• Confirm with technetium uptake if possible but don’t wait to treat if this isn’t possible

Treatment

• IV 0.9% saline 500ml/4hr
• NG tube if vomiting
• Take blood for T3, T4 and blood cultures if infection is suspected
• If there is no contraindication give propanolol 40mg/8hr  - give a max of 1mg/min, repeated up to 9 times at >2 min intervals
• Antithyroid drugs – carbimazole 15-25mg/6hr. After 4hr give Lugol’s solution (iodine) 0.3ml/8hr PO for 1 week to block thyroid
• Give hydrocortisone 100mg/6hr IV or dexamethasone 4mg/6hr PO
• Treat suspected infection e.g. cefuroxime 1.5g/8hr
• Adjust IV fluids as necessary, cool with tepid sponging and paracetamol

Continuing treatment

• After 5 days reduce carbimazole to 15mg/8hr PO
• After 10 days stop propranolol and iodine and adjust carbimazole