Thyrotoxicosis

Question 1

What is thyrotoxicosis?

Answer 1

Symptoms caused by the excessive circulation of thyroid hormones

Question 2

What can cause thyrotoxicosis?

Answer 2

Primary causes of hyperthyroidism originate from the thyroid gland itself and include:
1. Grave’s disease: Resulting from autoimmune stimulation of the thyroid gland by TSH receptor auto-antibodies.
2. Toxic adenoma: Adenoma that produces thyroid hormones.
3. Toxic multinodular goitre: Multiple thyroid nodules that produce thyroid hormones, leading to goitre.
4. Medications: Such as amiodarone.
5. Thyroiditis: Inflammation of the thyroid gland, e.g., de Quervain’s thyroiditis.
6. Radiation exposure

Secondary causes of hyperthyroidism, or those not caused by thyroid dysfunction, include:
1. Amiodarone
2. Lithium
3. TSH producing pituitary adenoma
4. Choriocarcinoma (beta-hCG can activate TSH receptors)
5. Gestational hyperthyroidism
6. Pituitary resistance to thyroxine (i.e., failure of negative feedback)
7. Struma ovarii (ectopic thyroid tissue in ovarian tumours)

Question 3

Describe the epidemiology of thyrotoxicosis

Answer 3

F>M (5:1), Graves’ Disease presents at 20-30 yrs old

Question 4

What are the presenting symptoms of thyrotoxicosis?

Answer 4

1. General → weight loss, restlessness, heat intolerance
2. Cardiac → palpitations, tachycardia
3. Skin → increased sweating, pretibial myxoedema (specific to graves), onycholysis
4. Diarrhoea, Anxiety, Tremor, Oligo/Amenorrhoea
5. Graves Specific ⇒ exophthalmos, pretibial myxoedema, thyroid acropachy (clubbing of fingernails)

Question 5

What investigations are used to diagnose/ monitor thyrotoxicosis?

Answer 5

1. TFTs → high T3/T4, low TSH
2. Anti-TSH Receptor Ab → if present, diagnosis is Graves’ Disease
3. Thyroid Ultrasound
4. Fine Needle Aspiration for neck lumps
5. Radioactive Iodine Uptake:
   - Diffuse Uptake throughout enlarged gland (nontender) ⇒ Grave’s Disease
   - Multinodular Gland with single hot nodule, patchy uptake ⇒ Toxic Multinodular Goitre (Tx with radioiodine therapy)
   - Diffuse Uptake with single cold nodule ⇒ Thyroid Cancer
   - No Uptake → de quervain’s (viral) thyroiditis
   *Initally are hyperthyroid and have painful goitre after a viral (flu-like) illness. Then become hypothyroid after.
   *Will have painful/tender goitre (in hyperthyroid stage)
   *Self-limiting and can be managed conservatively (ie. with NSAIDs).

Question 6

How is thyrotoxicosis managed?

Answer 6

a. Symptomatic Therapy (Immediate control of symptoms) → Propanolol (Beta-Blockers)
b. Definitive Therapy:
1. Anti-Thyroid Drugs → Carbimazole (inhibits TPO), Propylthiouracil, Potassium Iodide
- indicated in AF and osteoporosis
- Carbimazole is contraindicated in early pregnancy. Propylthiouracil is treatment of choice in first trimester pregnancy/thyroid storm.
- Carbimazole may cause agranulocytosis, which can lead to neutropenia and severe sepsis. A sore throat is an early (but non-specific sign) of infection- need to monitor via blood tests (FBC). Seek urgent medical attention if infection developed.
2. Radioactive Iodine Ablation → destruction of thyroid tissue via radioactive iodine. Used if resistant to antithyroid drugs.
- Definitive treatment for Grave’s Disease
3. Thyroid Surgery (Total Thyroidectomy)
4. Thyroid Storm → acute exacerbation of hyperthyroidism that results in a life-threatening hypermetabolic state (may be triggered by surgery, trauma or infection). Hyperpyrexia, tachycardia, hypotension, shock, abdominal pain, severe N&V.
5. Mx ⇒ IV propranolol, IV digoxin, propylthiouracil (followed by Lugol’s iodine 6hrs later), prednisolone/hydrocortisone

Question 7

What complications may arise from thryotoxicosis?

Answer 7

high output cardiac failure