T1 L8 Thyroid disease: hyper, hypo and other Flashcards
What is hypothyroidism?
Underproduction of thyroid hormone
What is hyperthyroidism?
Overproduction of thyroid hormone
What is thyrotoxicosis?
Overproduction of thyroid hormone (hyperthyroidism)
What is euthyroid?
Normal production of thyroid hormone
What is a goitre?
Enlargement of the thyroid gland
How to examine the thyroid?
Feel for thyroid cartilage then move down and lateral Moves on swallowing Listen for bruit Retrosternal extension Check cervical lymph node system
What are the normal ranges for a thyroid function test?
TSH: 0.3-4.2mu/l
FT4: 12-22pmol/l
FT3: 3.1-6.8pmol/l
Why doesn’t a negative autoantibody result exclude autoimmune disease?
May have different antibodies that aren’t tested for
Presence only helps to confirm a diagnosis
What are the different types of thyroid autoantibodies?
Destructive
Stimulatory
What is a destructive thyroid autoantibody?
Target thyroid for autoimmune destruction
What is a stimulatory thyroid autoantibody?
Stimulates TSH receptor
What are the symptoms of hypothyroidism?
Lethargy Weight gain Cold intolerance Constipation Facial puffiness Dry skin Hair loss Hoarseness Heavy menstrual periods
What are the signs of severe hypothyroidism?
Change in appearance Periorbital oedema Dry, flaking skin Diffuse hair loss Bradycardia Signs of median nerve compression Effusions Delayed relaxation of reflexes Croaky voice Goitre Stupor or coma
What are the causes of primary hypothyroidism?
Autoimmune hypothyroidism Hypothyroidism after treatment for hyperthyroidism Thyroiditis Drugs Congenital hypothyroidism Iodine deficiency
What are the clinical results for primary hypothyroidism?
Increased TSH
Decreased T4
Decreased T3
What are the causes of secondary hypothyroidism?
Diseases of hypothalamus or pituitary
What are the clinical results for secondary hypothyroidism?
Decreased TSH
Decreased T4
Decreased T3
Describe autoimmune hypothyroidism
Chronic autoimmune thyroiditis: Hashimoto’s
Myxoedema
What is myxoedema?
Accumulation of glycosaminoglycans in interstitial spaces of tissue
What are the symptoms of hyperthyroidism?
Weight loss Lack of energy Heat intolerance Anxiety / irritability Increased sweating Increased appetite Thirst Palpitations Pruritus Weight gain Loose bowels Oligomenorrhoea
What are the signs of hyperthyroidism?
Tremor Warm, moist skin Sinus tachycardia Atrial fibrillation Brisk reflexes Eye signs Thyroid bruit Muscle weakness Atrial fibrillation
What are the eye signs of hyperthyroidism?
Lid retraction
Proptosis
Ophthalmoplegia
Inflammation of conjunctiva
What are the causes of hyperthyroidism?
Autoimmune hyperthyroidism Toxic multimodule goitre Toxic adenoma Thyroiditis Drugs e.g. amiodarone
Why does gestational thyrotoxicosis occur?
Placental HCG is structurally similar to TSH
More common if hyperemesis / twin pregnancy
What is thyroid eye disease?
Inflammation of all orbital tissues except the eye
What are some mild symptoms of thyroid eye disease?
Itchy / dry eyes
Prominent eyes / change in appearance / proptosis
What are some more severe symptoms of thyroid eye disease?
Diplopia / loss of sight Loss of colour vision Redness / swelling of conjunctiva Unable to fully close eye Ache / pain / tightness behind eye
What is the active treatment for thyroid eye disease?
Encourage smoking cessation
Steroids
Immunosuppressive / steroid-sparing agents
Radiotherapy
What are the surgical treatments for thyroid eye disease?
Orbital decompression
Eyelid surgery
What is thyroid eye disease associated with in 20%?
Graves disease
What increases the likelihood of Graves disease?
Personal or family history of autoimmune thyroid / endocrine disease
Goitre with a bruit
Thyroid eye disease
Positive thyroid autoantibody titre
Describe the thyroid function test results in hyperthyroidism
Low TSH
Raised FT4
Raised FT3
TSH-receptor autoantibodies (Graves disease)
What further investigations may be done in hyperthyroidism?
Thyroid autoantibodies
Thyroid uptake scan
What is the medical treatment for Graves disease?
Carbimazole or propylthiouracil 18 to 24 months Titrate or block replace 1/3 have long term cure rate 2/3 will relapse
What are the risks of surgical treatment for Graves disease?
Anaesthetic Neck scar Hypothyroidism Hypoparathyroidism Vocal cord palsy due to recurrent laryngeal nerve damage
What are the risks if no treatment is given for Graves disease?
Symptoms worsen
Atrial fibrillation - stroke
Osteoporosis - fractures
What is a thyrotoxic crisis (thyroid storm)?
Associated with under or over treated hyperthyroidism
Heart rate, BP, temperature soar to extreme levels
What increases the likelihood of a thyrotoxic crisis?
Incompletely treated hyperthyroidism Start-stop Erratic compliance Early on in course of treatment Surgery / radioiodine treatment without adequate preparation
What triggers a thyrotoxic crisis?
Surgery
Childbirth
Acute severe illness: infection, trauma, diabetic ketoacidosis, stroke, PE
What is thyroiditis?
Self-limiting thyroid disease
Transient mild thyrotoxicosis
Resolves in 1-2 months
Give beta blockers if required
Longer hypothyroid phase
Last 4-6 months
May require thyroxine treatment for a while
When should thyroiditis be considered?
If patient is pregnant or 1 year postpartum
Diabetes, family history of thyroid disease, smoker
Tender thyroid
Clinical thyroid status doesn’t fit with lab results
No diagnostic features of Graves disease
Current / recent treatment with immunomodulatory medication
What other diseases are associated with thyroid disease?
Type I diabetes Pernicious anaemia Coeliac disease Premature ovarian failure Addison's disease Turner syndrome Down's syndrome Medications: lithium, amiodarone
