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Hyperthyroidism

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(1) from the hypothalamus stimulates (2) release from the (3 - anterior or posterior?) pituitary, which stimulates T3 and T4 release by the thyroid gland
1. TRH - thyrotropin releasing hormone
2. TSH - thyroid-stimulating
3. anterior
What is subclinical hyperthyroidism?
Biochemical diagnosis
TSH low, free T3/ free T4 are normal
What are the top 3 causes of primary hyperthyroidism?
Graves disease
Toxic multinodular goitre
Toxic adenoma
What are the main symptoms of hyperthyroidism?
Hyperactivity, irritability
Heat intolerance/sweating
Palpitations
Fatigue, weakness
Weight loss but increased appetite
DIarrhoea
Polyuria
Oligomenorrhoea
Loss of libido
[source: Harrisons - descending order of frequency]
What are the most frequent signs of hyperthyroidism?
Tachycardia/AF
Tremor
Goitre
Warm/moist skin
Muscle weakness, proximal myopathy
Lid retraction/lid lag
Gynaecomastia
[source: Harrisons - descending order of frequency]
What are the INITIAL investigations you would perform in a patient you suspect might be hyperthyroid from history/exam?
TSH
If normal, not thyroid dysfunction
If TSH low, free T3/ free T4
Your patient has a low TSH, high fT3/fT4. What antibodies should you request? Why?
TSH-receptor antibody (TRAb) - Graves
Anti-thyroperoxidase (anti-TPO) - Hashimoto's, Graves, nodular goitre, cancer
Thyroglobulin antibodies (less useful - mostly used in monitoring for cancer recurrence post-thyroidectomy)

(Don't just write "thyroid antibodies" on a path slip! Never works!)
When would you order an ultrasound in a hyperthyroid patient?
When you're worried about cancer (eg rapid growth, asymmetrical, focal firmness, goitre but normal TSH, negative antibodies)
Also consider FNA if worried about cancer (can write "USS +/- FNA" on the request and let radiologist decide)
If the TSH is subnormal, what would be your imaging of choice?
Radionuclide thyroid scan (A.K.A. scintigraphy/isotope scan)
Broadly, what are the three management options for thyrotoxicosis?
- Thionamides (carbimazole or PTU - carbimazole is better because PTU can cause fatal hepatotoxicity)
- Radioactive iodine ablation
- Surgery
What are the indications for treatment of subclinical hyperthyroidism?
- TSH <0.1 - "fully suppressed"
- Multinodular goitre
- Pre-existing osteoporosis or heart disease
- Older patients

(in everyone else, just re-test in 6-12 weeks and values will normalise in ~1/3 of patients)
Epidemiology of Graves disease - sex, age?
Females 20-50 years old
(Like many other autoimmune conditions)
Examination findings in Graves disease?
Usual signs of hyperthyroidism
Diffuse, smooth, rubbery goitre with a bruit
Ophthalmopathy may be present - only proptosis is specific to Graves disease (lid lag is not specific)
Management of Graves disease?
Carbimazole for a year or two if not contraindicated - may achieve remission
If not, consider radioactive iodine ablation or thyroidectomy
Are nodules in toxic multinodular goitre and toxic adenoma autonomous or do they respond to regulation from TSH?
They are autonomous - this is what "toxic" means - they produce thyroid hormone independently of TSH
Neck pain + malaise + low TSH = ?
Most likely subacute thyroiditis
Clinical course of subacute thyroiditis?
6 weeks thyrotoxicosis, followed by ~6 weeks of hypothyroidism, then resolution