Thyroid Disease
FY1 Sejal Nirban
Thyroid Gland
Predominantly secretes T4 and small amounts of T3
Most T3 is produced by peripheral conversion of T4
Iodine is an essential requirement for thyroid hormone synthesis
99% of T4 and T3 circulate bound to plasma proteins (Thyroid Binding Globulin)
Free hormones are available to control the metabolic rate of many tissues
Thyroid function is measured using Serum TSH and free T4 and T3
Hyperthyroidism
Affects 1/50 females and 1/250 males
Due to an excess of T3 and T4 causing thyrotoxicosis
An acute exacerbation of symptoms is called a thyrotoxic crisis- usually brought on by infection
Diagnosis is made by measuring TSH, free T3 and free T4
Raised TSH suggests the fault is in the pituitary or hypothalamus whereas low TSH is due to a thyroid
problem
 Symptoms
 Weight loss
 Increased appetite
 Heat intolerance
 Palpitations
 Fatigue
 Sweating
 Diarrhoea
 Oligomenorrhoea
 Psychiatric symptoms
 Irritability
 Emotional lability
 Psychosis
 Signs
 General
 Hair thinning
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Goitre
Lid lag, lid retraction
Pre-tibial myxoedema
Eye signs
Palmar erythema
 CVS
 Tachycardia
 AF
 Neuro
 Fine tremor
Causes:
1. Graves Disease- most common cause. IgG antibodies bind to TSH receptor
stimulating thyroid hormone production
2. Toxic Multinodular Goitre
3. Solitary adenoma
4. De Quervains Thyroiditis- acute inflammation of thyroid gland (fever, malaise and
neck pain)
5. Postpartum thyroiditis
Management:
1. Anti-thyroid drugs: Carbimazole (UK) Methimazole (USA)- both block thyroid hormone
biosynthesis and also have immunosuppressive affects. Clinical benefit is not seen for 10-20
days. Carbimazole can cause agranulocytisis- seek urgent blood count if patient develops
unexplained fever or sore throat
2. Beta blockers: Propanolol used for symptomatic control
3. Radioactive Iodine: contraindicated in pregnancy and breast feeding. Accumulates in the
gland and results in local irridation
4. Surgery: thyroidectomy can only be performed in euthyroid patients. Complications of
surgery include bleeding, hypocalcaemia and hypothyroidism.
Thyroid Storm
Life threatening condition- severe thyrotoxicosis
Precipitated by infection, stress and surgery
Treated with large doses of carbimazole, propranolol, potassium iodide and hydrocortisone
Graves’ Disease
Goitre
Eye signs- oedema, proptosis, lid retraction, lid lag, and opthalmoplegia- worse in smokers.
Thyrotoxicosis
Cause: T lymphocytes react with antigens shared by the orbit and thyroid leads to retro orbital
inflammation. Swelling and oedema of extra-ocular muscles leading to limitation of movement and
proptosis. Increased pressure on the optic nerve may cause optic atrophy.
Treatment is low dose of carbimazole, surgery or radioiodine and stop smoking advice
Hypothyroidism
Affects 1/100 females and 1/500 males. Incidence increases with age.
T3 and T4 levels are low with a raised TSH
If TSH is low then there is likely to be a hypothalamic or pituitary lesion
 Symptoms
 Weight gain
 Fatigue, lethargy
 Cold intolerance
 Constipation
 Menorrhagia
 Hoarse voice
 Myalgia
 Carpal tunnel syndrome
 Psychiatric symptoms
 Depression
 Dementia
 Signs
 General
 Dry skin and hair
 Goitre
 Non-pitting oedema
 Facial features – purple lips, malar flush, periorbital oedema, lateral
eyebrow loss
 CVS
 Bradycardia
 Neuro
 Cerebellar ataxia
 Slow relaxing reflexes
 Peripheral neuropathy
Causes
1.
2.
3.
4.
5.
Iodine deficiency
Autoimmune thyroiditis- Hashimoto’s thyroiditis
Iatrogenic- thyroidectomy, radioactive iodine
Drug induced- carbimazole, lithium, Amiodarone
Congenital hypothyroidism- thyroid aplasia
Management: Lifelong Levothyroxine. Aim to normalise TSH
Myxoedema coma
Severe hypothyroidism with swelling of subcutaneous tissues- typically around eyes and back of
hands ‘’bunch of banana hands’’
Unresponsive, decreased respiratory rate, low bp, low glucose, low temperature
Pregnancy and Thyroid
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Increased concentration of TBG
Total T4 and T3 increase
Free T4 and T3 remain within normal range
TSH does not change
Two pregnancy-related hormones—human chorionic gonadotropin (hCG) and estrogen—cause
increased thyroid hormone levels in the blood. Made by the placenta, hCG is similar to TSH and
mildly stimulates the thyroid to produce more thyroid hormone. Increased estrogen produces higher
levels of thyroid-binding globulin.
Transient autoimmune thyroiditis can occur postpartum resulting in hypo or hyperthyroidism
Hyperthyroid management: Propylthiouracil. Carbimazole is associated with congenital defects
including aplasia cutis of the neonate.
Hypothyroid management: Levothyroxine is safe to give in pregnancy
Thyroid Malignancy
Most present as asymptomatic thyroid nodules
Types:
1.
2.
3.
4.
5.
Papillary- 70%. Good prognosis
Follicular- 20%. Good prognosis
Anaplastic <5%. Aggressive, poor prognosis
Lymphoma 2%. Poor prognosis
Medullary 5%. Often familial. Poor prognosis
Investigation: FNAC distinguishes between benign and malignant nodules
Treatment: Radioactive iodine, thyroidectomy with wide local lymph node excision. External
radiotherapy and palliative care for anaplastic and lymphomas.