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Hyperthyroidism
Endocrinology series
Dr Azeem Alam, MBBS BSc (Hons)Surgical AFPGuy’s and St. Thomas’ HospitalContent reviewed on the 26/04/2020.
Pathophysiology, differentials, investigations and management.
Cases Quiz
History
A 45-year-old lady presents to the GP with a 1-month history of ‘hot flushes’. She is very anxious and on occasion feels her chest thumping. Her clothes no longer fit, and she wonders if her symptoms could be due to menopause.
On examination, she has a 2 cm diffuse neck swelling.
Observations
HR 101, BP 138/98, RR 18, SpO2 99%, Temp 37.8°C.
2
Case 1
History
A 45-year-old lady presents to the GP with a 1-month history of ‘hot flushes’. She is very anxious and on occasion feels her chest thumping. Her clothes no longer fit, and she wonders if her symptoms could be due to menopause.
On examination, she has a 2 cm diffuse neck swelling.
Observations
HR 101, BP 138/98, RR 18, SpO2 99%, Temp 37.8°C.
4
Case 1
4
Pathophysiology
5
Definition: hyperthyroidism reflects an increased level of circulating thyroid hormones, leading to raised metabolic rate and sympathetic nervous system activation.
Pathophysiology
(1)
Pathophysiology
6
Pathophysiology
Pathophysiology
7
Primary hyperthyroidism• Excessive production of T3/T4 by the thyroid gland • Thyroid gland pathology• Most common subtype
Secondary hyperthyroidism• Stimulation of the thyroid gland by excessive TSH • Originates due to pathology of the pituitary or hypothalamus • May also be secondary to a TSH-secreting tumour
Pathophysiology
(1)
Pathophysiology
8
Graves’ disease• Anti-TSH receptor antibodies• Most common cause of hyperthyroidism
(75%)• Diffuse goitre and thyroid eye signs
Primary hyperthyroidism
Toxic multinodular goitre• Iodine deficiency• Compensatory TSH secretion • Nodular goitre formation• Nodules become TSH-independent and
thyroid hormones
(2)
Pathophysiology
9
Primary hyperthyroidism
Toxic adenoma Thyroiditis• Single autonomous functional
nodule• Initial stage will include transient
hyperthyroidism • Hypothyroidism is the final stage• Hashimoto’s and De Quervain’s
thyroiditis
Subclinical hyperthyroidism Drugs• Normal T3/T4, low TSH• May be due to any of the above
causes• Typically due to toxic multinodular
goitre or Graves’ disease
• Amiodarone: causes both hyperthyroidism and hypothyroidism
Pathophysiology
10
Pituitary adenoma Ectopic tumour Hypothalamic tumour• TSH-secreting pituitary
adenoma• hCG-secreting tumours (e.g.
choriocarcinoma)• Excessive TRH secretion• Rare cause of
hyperthyroidism
Secondary hyperthyroidism
Choriocarcinoma(3)
11
Risk factors
• Female gender: particularly for Graves’ disease
• Family history
• Other autoimmune conditions
• Smoking: increases risk of Graves’ eye disease
• Trauma to the thyroid: including surgery
• Drugs: e.g. amiodarone
Pathophysiology
12
Clinical features
Symptoms SignsWeight loss Postural tremorHeat intolerance and sweating
Palmar erythema
Palpitations Graves’ disease• Thyroid acropachy• Pretibial myxedema• Eye signs
• Exophthalmos• Ophthalmoplegia
Menstrual irregularity Lid lag and retraction Anxiety Goitre
Hyperreflexia
THYROIDISM Mnemonic
TremorHeart rate increaseYawningRestlessOligomenorrhoeaIrritabilityDiarrhoeaIntolerance to heatSweatingMuscle wasting (weight loss)
Pathophysiology
13
Clinical features: general
(4) Goitre
14
Clinical features: Graves’ disease
No signs
Only signs no symptoms
Soft tissue involvement
Proptosis
Extraocular muscle involvement (ophthalmoplegia)
Corneal involvement
Sight loss
Pretibial myxedema
Exophthalmos
Thyroid acropachy
(5)
(5)
(6)
16
Investigations: stable patient
Thyroid autoantibodiesAutoantibody Condition PrevalenceAnti-TSH receptor Graves’ disease 90-100%
Hashimoto’s thyroiditis 0-5%
Anti-TPO Graves’ disease 70-80%
Hashimoto’s thyroiditis 90-95%
Anti-thyroglobulin Graves’ disease 20-40%
Hashimoto’s thyroiditis 30-50%
17
Investigations: stable patient
Primary investigations:• Thyroid function tests (TFTs): first-line investigation• Antibodies: anti-TSH receptor antibodies (95%) and anti-TPO most often raised in
Graves’ disease
Investigations to consider:• Ultrasound: if thyrotoxic with have a palpable thyroid nodule• Technetium radionuclide scan: performed if anti-TSH antibodies are negative• Glucose: hyperthyroidism is associated with hyperglycaemia• ECG: hyperthyroidism is associated with atrial fibrillation
TSH T4 Cause↓ ↑ Primary hyperthyroidism: e.g. Graves’ disease↓ ↔ Subclinical hyperthyroidism↑ ↑ Secondary hyperthyroidism: e.g. TSH-secreting pituitary
adenoma↔ ↑
18
Investigations: stable patient
(7)
21
Management
Antithyroid medication:• Carbimazole: usually first-line• Propylthiouracil: first-line pre-pregnancy or in the first trimester• Titration regime: titrate down to lowest effective dose
• Please note that there was a discrepancy previously regarding the titration regimen. This has now been rectified.
• Block and replace regimen: levothyroxine is added as needed
Radioiodine:• First-line definitive management in Graves' and toxic multinodular goitre• Contraindicated in pregnancy and breastfeeding• Offer patient advice
Surgery: total or hemithyroidectomy• Requires pre-operative optimisation• Be aware of the risks
Other: consider propranolol for symptomatic relief
Pathophysiology
22
Thyroid storm
Aetiology• Untreated hyperthyroidism • Often provoked by infection
Clinical features• Tachycardia: often > 140 BPM, with or without AF• High temperature: often > 40°C• Diarrhoea and vomiting• Jaundice• Confusion or mental agitation
Mortality rate• With treatment, 20-40% • Untreated, up to 75%
23
Investigations: thyroid storm
Primary investigations• TFTs: elevated T3 and T4, suppressed TSH• Screen for the cause: e.g. an infection screen• Full set of bloods: FBC, U&Es, LFTs, bone profile, blood glucose• CXR• Arterial blood gases
TSH T4 Cause↓ ↑ Primary hyperthyroidism: e.g. Graves’ disease↓ ↔ Subclinical hyperthyroidism↑ ↑ Secondary hyperthyroidism: e.g. TSH-secreting pituitary
adenoma↔ ↑
24
Management: thyroid storm
Emergency• IV fluids: replace losses• NG tube insertion: if vomiting• Cooling: sponging and paracetamol
• Antithyroid drugs: propylthiouracil is often preferred• Corticosteroid: IV hydrocortisone• Beta-blocker: propranolol PO or IV over 10 minutes• Oral iodine: Lugol’s iodine offered >1 hour after propylthiouracil
• Sedation: if required, use chlorpromazine• Plasma exchange or thyroidectomy: in refractory patients
Pathophysiology
26
Recap
• Graves’ disease is the most common cause of hyperthyroidism
• Graves’ disease occurs due to anti-TSH receptor antibodies
• Patients often present with palpitations, weight loss and height intolerance
• Graves’ may present with eye disease
• Initial investigations are TFTs and autoantibodies
• Additional investigations include ultrasound and Technetium radionuclide scanning
• Thyroid storm is a life-threatening manifestation of thyrotoxicosis
History
A 55-year-old lady is currently on chemotherapy for ovarian cancer. She presents to the GP with an ongoing history of palpitations that are particularly worse at night. Her friends have told her she has lost weight and her clothes are loose.
The GP checks her TFTs: low TSH and raised T3/T4.
Observations
HR 99, BP 148/98, RR 18, SpO2 99%, Temp 37.5°C.
27
Case 2
History
A 55-year-old lady is currently on chemotherapy for ovarian cancer. She presents to the GP with an ongoing history of palpitations that are particularly worse at night. Her friends have told her she has lost weight and her clothes are loose.
The GP checks her TFTs: low TSH and raised T3/T4.
Observations
HR 99, BP 148/98, RR 18, SpO2 99%, Temp 37.5°C.
29
Case 2
30
Top decile question
32
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References
1. Mikael Häggström / Public domain2. Blausen.com staff (2014). Medical gallery of Blausen Medical 2014;. WikiJournal of Medicine 1 (2).
DOI:10.15347/wjm/2014.010. ISSN 2002-4436. / CC BY (https://creativecommons.org/licenses/by/3.0)3. Nephron / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)4. Drahreg01 / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)5. Herbert L. Fred, MD and Hendrik A. van Dijk / CC BY (https://creativecommons.org/licenses/by/2.0)6. Jonathan Trobe, M.D. - University of Michigan Kellogg Eye Center / CC BY
(https://creativecommons.org/licenses/by/3.0)7. Petros Perros / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)
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