Thyroid Pathology Flashcards
What is the function of thyroid hormone?
>Cell Basal Metabolic Rate
>CO
>Bone Resorption
Activates sympathetic nervous system
What hormone is thyroid hormone permissive to?
Adrenalin
Describe the pathophysiology of Grave’s disease
Antibodies are produced which mimic TSH and continually activates the thyroid gland
This increased TH production switches off TSH release and so plasma concentration is low
Thyroid gland may be 2-3X normal size due to hyperplasia and hyperactive cells may also be apparent
What sex is hyperthyroidism more common?
F>M
What are the causes of hyperthyroidism?
Graves
Thyroid Adenoma
Toxic Multinodular Goitre
Secondary: Pituitary adenoma
Drugs
Struma Ovarii: Rare ovarian cancer
(Initial De Quervain’s)
What drugs can cause hyperthyroidism?
Amiodarone
Lithium
What is the most common cause of hyperthyroidism?
Graves (70% causes)
How does hyperthyroidism present?
Tremor
Weight loss
Palpitations
Hair loss
Poor concentration
Amenorrhea/oligomennnorhoea
Bowel frequency
Sweaty
Heat Intolerance
Exophthalmos/Proptosis
Pretibial myxoedema
Muscle weakness
Clubbing
Anxiety/irritability
Hyperreflexia
>HR/Tachycardia
Goitre
What is a goitre?
Enlargement of the thyroid gland that can accompany hypo and hyperthyroidism
What investigations are used in hyperthyroidism diagnosis?
TSH
Increased unbound T3/T4
Radioactive Iodine Uptake Test and Thyroid Scan
- Patchy uptake suggests toxic multinodular goitre
Antibodies
- Thyroid Peroxidase Antibodies
- TSH Receptor Antibodies, present in 90-100% Graves patients
When is TSH high for hyperthyroidism?
Secondary/pituitary causes of hyperthyroidism
When is TSH low for hyperthyroidism?
Primary causes of hyperthyroidism
Give complications of hyperthyroidism
Atrial fibrillation
HF
Osteoporosis
How is hyperthyroidism managed?
Anti-thyroid drugs
Radio-iodine therapy: For patients >45
Partial thyroidectomy
B-Blockers: Symptomatic relief
Give an example of an anti-thyroid drug?
Carbimazole
What is thyroid storm?
Hypermetabolism when individual causing exacerbation of symptoms
Describe the pathophysiology of Hashimoto’s
Autoimmune destruction of thyroid epithelial cells, involving T cells, cytokine and antibody mediated destruction (circulating antibodies to thyroglobulin and thyroid peroxidase)
This results in diffuse enlargement of the thyroid and then the eventual shrinkage and gradual failure
How common is hypothyroidism?
Most common endocrine condition after diabetes
What sex is hypothyroidism most common?
F>M
What are the primary causes of hypothyroidism?
Hashimoto’s Disease
Deficiency in dietary iodine
- Milk, seafood, seaweed
Iatrogenic
- External radiation
- Post-operative/post-radioactive iodine
Congenital
Post-subacute Thyroiditis/De Quervain’s
- Post-infection
What is Hashimoto’s disease?
Autoimmune attack of thyroid gland
What are the secondary causes of hypothyroidism?
Pituitary tumour
Craniopharyngioma
Post pituitary surgery or radiotherapy
Sheehan’s Syndrome
Isolated TRH Deficiency
What is Sheehan’s Syndrome?
Postpartum pituitary gland necrosis
How does hypothyroidism present?
Weight gain
Cold intolerance
Depression
Dry and thin hair/skin, brittle nails: Disrupted protein synthesis
Constipation
Menorrhagia
Hoarseness: Severe
Lethargy
Hyporeflexia: Altered nervous system
Bradycardia
Goitre: If Hashimoto
Puffy face, large tongue: Severe
Coma: Severe
What investigations are used in hypothyroidism diagnosis?
TSH
Anti Thyroid Peroxidase antibodies
FBC
- Macrocytic anaemia
>ESR in De Quervain’s
Iodine uptake scan
- Reduced iodine uptake in De Quervain’s
When is TSH high for hypothyroidism?
Primary
When is TSH low/normal for hypothyroidism?
secondary
How is hypothyroidism managed?
Levothyroxine: T4 tablets
Liothyronine: T3 tablets
When is subclinical hypothyroidism treated?
Treat if TSH>10 or >5 with positive thyroid antibodies
Trial therapy if TSH elevated with symptoms
What is Myxoedema Coma?
Severe life-threatening form of hypothyroidism affecting those with poorly controlled hypothyroidism in a physiological stressful situation
Describe how levothyroxine is given
T4 tablets, initial dose of 50cmg/day
Increase after 2 weeks to 100mcg and continue until TSH is normal
What are the classifications of thyroid tumour?
Papillary carcinoma
Follicular carcinoma
Anaplastic carcinoma
Medullary carcinoma
Lymphoma
What is the most common thyroid tumour?
Papillary carcinoma, most common at 75-80%
Give side effects of Carbimazole
Agranulocytosis
Hair loss
Headaches
Nausea
Stomach pains
Itchy skin
Rashes
Muscle and joint pain
What is the most serious side effect of Carbimazole?
Bone marrow suppression (neutropenia/agranulocytosis) resulting in immune system suppression
Sore throat is the most common symptom of this
What is the mechanism of action of Carbimazole?
Blocks thyroid peroxidase from coupling and iodinating the tyrosine residues on thyroglobulin, therefore reducing thyroid hormone production
How is Carbimazole given?
High doses for 6 weeks until patient becomes euthyroid before being reduced
What group of patients is papillary carcinoma most common in?
Young females
What is the prognosis of papillary carcinoma?
Excellent
What is associated with medullary carcinoma?
MEN2
What does medullary carcinoma secrete?
Calcitonin
This used as an alternative to thyroglobulin in medullary carcinoma for recurrence screening
How are thyroid tumours managed?
Total thyroidectomy followed by radioiodine
What histological sign is seen in papillary thyroid cancer?
Orphan annie cells
What levels are measured yearly to detect early recurring thyroid tumours?
Thyroglobulin
What sign is only seen in Graves disease?
Exopthalamos/Proptosis
Give complications of Hashimotos
MALT Lymphoma
Addisons
Graves
Type 1 diabetes
Pernicious anaemia
Lupus Erythematosus
RA
Thrombocytopenic Purpura
Vitiligo
How do thyroid tumours present?
PAID DUET
Pain in the neck
Asymmetry in the thyroid
Increased risk for women
Difficulty swallowing
Dyspnoea
Unexplained hoarseness
Enlarged lymph nodes in neck
Thyroid nodule/lump
Can Carbimazole be used in pregnancy?
Contraindicated in first trimester as can cross placenta and cause aplasia cutis
How does myxoedema coma present?
Confusion
Hypothermia
Hypotension
Bradycardia
How is myxoedema coma managed?
IV thyroid replacement
IV corticosteroids, until the possibility of coexisting adrenal insufficiency has been excluded
IV fluids
Electrolyte imbalance correction
Rewarming
What are the features of thyroid eye disease?
Proptosis
Lagophthalamos, inability to fully close eyelids
Lid retraction
Opthalmoplegia
What is the first line therapy for toxic multinodular goitre?
radio-iodine therapy
How can thyroid eye disease be prevented?
stop smoking
(this is a risk factor for Graves)
How much should levothyroxine dose be increased in pregnancy?
Up to 50% as early as 4-6 weeks
When should levothyroixine be adjusted?
Higher dose for pregnancy and lower in ischaemic heart disease
Give causes of thyroid storm
Stops treatment
Infection
Surgery
Trauma
Acute iodine load
How does thyroid storm present?
Fever over 38.5ºC
Tachycardia
Confusion and agitation
N&V
Hypertension
HF
Abnormal LFT/jaundice
How is thyroid storm managed?
Symptomatic treatment, paracetamol
Treatment of underlying precipitating event
B blockers, typically IV propranolol
Anti-thyroid drugs, methimazole
Lugol’s iodine
Dexamethasone, blocks the conversion of T4 to T3
What is first line management of thyroid storm?
IV B blocker
What blood test is used to measure response to treatment in Hashimotos?
TSH
What is the most common cause of hypothyroidism
Iodine deficiency worldwide
Hashimotos in countries were iodine consumption is adequate
How does goitre presentation differentiate in hypothyroidism?
Hashimotos is associated with non tender goitre
De Quervain’s is associated with a painful goitre
Describe the TFT results in non thyroidal illness/sick euthyroid syndrome
TSH low (sometimes this is normal) and free T4 low
Common in elderly hospital inpatients
Changes are reversible upon recovery from the systemic illness and hence no treatment is usually needed
Describe the TFT results in subclinical hypothyroidism
TSH high and free T4 normal
Describe the TFT results in patients with poor compliance with levothyroxine
TSH high and normal free T4
How can steroid therapy affect TFT results?
TSH low and normal free T4
What group of patients is anaplastic thyroid carcinoma most common in?
Elderly females
What drug interactions can occur with levothyroxine?
Iron and calcium carbonate
Absorption of levothyroxine reduced, give at least 4 hours apart
Give side effects of thyroxine therapy
Hyperthyroidism
Osteoporosis
Worsening angina
AF
Give complications of thyroidectomy
Recurrent laryngeal nerve damage
Bleeding and therefore haematomas due to comfined space, rapidly leading to respiratory compromise due to laryngeal oedema
Parthyroid damage and hypocalcaemia
How is hyperthyroidism managed in pregnancy?
Propylthiouracil
