Thyroid Flashcards
What hormones can be measured to screen for thyroid disease?
TSH
T3 and 4
What hormone levels would you expect to find in hyperthyroidism?
What is the exception?
Low TSH
High T3&4
A pituitary adenoma secretes TSH, in which case TSH is high.
What hormone levels would you expect to find in hypothyroidism?
What is the exception?
High TSH
Low T3&4
Secondary hypothyroidism is the exception e.g. a pituitary or hypothalamic cause of the hypothyroid, in which case TSH would be low.
What does thyrotoxicosis mean?
An abnormal and excessive quantity of thyroid hormone in the body.
Where is the pathology in primary hyperthyroidism?
Thyroid itself is behaving abnormally and producing excessive thyroid hormone.
Where is the pathology in secondary hyperthyroidism?
The hypothalamus or pituitary.
The thyroid is producing excessive thyroid hormone as a result of overstimulation by thyroid stimulating hormone.
Describe Grave’s disease
Autoimmune condition where TSH receptor antibodies cause a primary hyperthyroidism.
Describe toxic multinodular goitre (Plummer’s disease)
A condition where nodules develop on the thyroid gland that act independently of the normal feedback system and continuously produce excessive thyroid hormone. Primary hyperthyroidism .
What are the causes of hyperthyroidism?
Grave’s disease
Toxic multinodular goitre
Solitary toxic thyroid nodule
Thyroiditis (e.g. De Quervain’s, Hashimoto’s, postpartum and drug-induced thyroiditis)
What are the signs of hyperthyroidism specific to Grave’s?
Briefly describe the common pathophysiology
Reactions to the TSH receptor antibodies:
>Bilateral exophthalmos.
-inflammation, swelling and hypertrophy of the tissue behind the eyeball that forces the eyeball forward.
>Pretibial myxoedema.
-a dermatological condition where there are deposits of mucin under the skin on the anterior aspect of the leg (the pre-tibial area). This gives a discoloured, waxy, oedematous appearance to the skin over this area.
>Diffuse goitre, without nodules
>Graves’ eye disease.
What are the features of hyperthyroidism?
Anxiety and irritability Sweating and heat intolerance Tachycardia Weight loss Fatigue Frequent loose stools Sexual dysfunction
What are the signs of hyperthyroidism specific to toxic multinodular goitre?
Goitre with firm nodules.
Most patients are aged over 50.
Briefly describe De Quervain’s Thyroiditis
the presentation of a viral infection with fever, neck pain and tenderness, dysphagia and features of hyperthyroidism.
There is a hyperthyroid phase followed by a hypothyroid phase as the TSH level falls due to negative feedback.
Briefly describe how to manage De Quervain’s Thyroiditis
It is a self-limiting condition.
Supportive treatment:
NSAIDs for pain and inflammation.
Beta-blockers for symptomatic relief of hyperthyroidism.
Briefly describe the meaning of a thyroid storm
“thyrotoxic crisis”. It is a more severe presentation of hyperthyroidism with pyrexia, tachycardia and delirium.
What is the first line treatment of hyperthyroidism?
Carbimazole is the first line anti-thyroid drug.
What is the second line pharmacological treatment of hyperthyroidism?
Propylthiouracil is the second line anti-thyroid drug. It is used in a similar way to carbimazole.
There is a small risk of severe hepatic reactions, including death, which is why carbimazole is preferred.
What pharmacological options are there for symptom control of hyperthyroidism?
Beta blockers are used to block the adrenalin related symptoms of hyperthyroidism.
Propranolol is a good choice because it non-selectively blocks adrenergic activity as opposed to more “selective” beta blockers the work only on the heart.
What are the non-pharmacological treatment options of hyperthyroidism?
Treatment with radioactive iodine involves drinking a single dose of radioactive iodine. This is taken up by the thyroid gland and the emitted radiation destroys a proportion of the thyroid cells. Patients can be left hypothyroid afterwards and require levothyroxine replacement.
A definitive option is to surgically remove the whole thyroid or toxic nodules. Patients can be left hypothyroid afterwards and require levothyroxine replacement.
What are the causes of primary hypothyroidism?
Hashimoto’s Thyroiditis
Iodine Deficiency
Secondary to Treatment of Hyperthyroidism
Medications- Lithium inhibits the production of thyroid hormones in the thyroid gland and can cause a goitre and hypothyroidism.
- Amiodarone interferes with thyroid hormone production and metabolism, usually causing hypothyroidism but it can also cause thyrotoxicosis.
What are the causes of Secondary Hypothyroidism?
Hypopituitarism: Tumours Infection Vascular (e.g. Sheehan Syndrome) Radiation
Describe the presentation of hypothyroidism
Weight gain Fatigue Dry skin Coarse hair and hair loss Fluid retention (oedema, pleural effusions, ascites) Heavy or irregular periods Constipation
Describe the cause of Hashimoto’s thyroiditis
Autoimmune inflammation of the thyroid gland.
It is associated with antithyroid peroxidase (anti-TPO) antibodies and antithyroglobulin antibodies.
Describe the management of hypothyroidism
Oral levothyroxine: synthetic T4. This metabolizes to T3 in the body.
The dose is titrated until TSH levels are normal.
(If the TSH level is high, the dose is too low and needs to be increased.)
