D&E - Endocrinology Flashcards
Which hormones are released by the anterior pituitary gland?
- TSH
- ACTH
- FSH and LH
- GH
- prolactin
Which hormones are released by the posterior pituitary gland?
- oxytocin
- ADH
Describe the thyroid axis.
- Hypothalamus releases TRH
- TRH stimulates the anterior pituitary gland to release TSH
- TSH stimulates the thyroid gland to release T3 and T4
The thyroid axis is a negative feedback loop - as the end hormone rises (T3 and T4), the hypothalamus and anterior pituitary are suppressed.
What are the actions of thyroid hormones (T3 and T4)?
Thyroid hormones act upon intracellular thyroid receptors, TRa and TRb to:
- increase basal metabolic rate
- increase heart rate
- increasing temperature
Define:
a) hyperthyroidism
b) primary hyperthyroidism
c) secondary hyperthyroidism
d) thyrotoxicosis
a) the overproduction of thyroid hormones, T3 and T4, by the thyroid gland.
b) hyperthyroidism due to thyroid pathology
c) hyperthyroidism due to hypothalamic-pituitary pathology (excess TRH or TSH).
d) the effects of an abnormal and excessive quantity of thyroid hormones in the body.
What is Grave’s disease?
An autoimmune condition in which TSH receptor antibodies stimulate TSH receptors on the thyroid, causing a primary hyperthyroidism.
It is the most common cause of hyperthyroidism.
What is toxic multinodular goitre?
Nodular growths that are unregulated by the thyroid excess develop on the thyroid gland, producing excessive thyroid hormones.
What are the causes of hyperthyroidism?
GIST:
Graves disease
Inflammation (thyroiditis)
Solitary toxic thyroid nodule
Toxic multinodular goitre
What are the causes of thyroiditis?
De Quervain’s thyroiditis
Hashimotos thyroiditis
Postpartum thyroiditis
Drug-induced thyroiditis
Presentation of hyperthyroidism.
- anxiety and irritability
- sweating and heat intolerance
- tachycardia
- weight loss
- fatigue
- frequent loose stools
- sexual dysfunction
- insomnia
- tremor
- hyper-reflexia
What are the features of Grave’s disease?
Explain why these features manifest.
Diffuse goitre - due to TSH receptor stimulation by TSH autoantibodies.
Exopthalmos - TSH receptor stimulation behind the eyes by TSH autoantibodies, causing inflammation and swelling.
Pretibial myxoedema - TSH autoantibodies cause deposition of glycosaminoglycans under the skin in the pre-tibial area, giving an oedematous appearance.
What is a solitary toxic thyroid nodule?
A benign adenoma of the thyroid gland, causing excessive release of thyroid hormones.
Treatment is usually surgical removal of the nodule.
What are the phases of De Quervain’s thyroiditis?
A common condition causing temporary inflammation of the thyroid gland:
- Thyrotoxicosis (goitre, flu-like illness)
- Hypothyroidism
- Return to normal
What is the treatment of De Quervain’s thyroiditis?
NSAIDs for pain and inflammation.
Beta-blockers for the symptoms of hyperthyroidism.
Levothyroxine for the symptoms of hypothyroidism.
Presentation of thyrotoxic crisis.
A rare presentation of extreme hyperthyroidism:
- fever
- tachycardia
- delirium
What is the pharmacological treatment of hyperthyroidism?
1st line: Carbimazole
2nd line: Propylthiouracil
Note beta blockers can be used to relieve symptoms of hyperthyroidism.
Give the side effect profiles of carbimazole and propylthiouracil.
Carbimazole:
- acute pancreatitis
- bone marrow suppression (immunosuppression)
Propylthiouracil:
- bone marrow suppression (immunosuppression)
Outline the mechanism of action of radioactive iodine in the treatment of hyperthyroidism.
Radioactive iodine destroys a proportion of thyroid cells, resulting in the reduced production of thyroid hormones.
Remission can take 6 months, and includes hypothyroidism. Therefore, long-term levothyroxine is often required.
What are the effects of thyroidectomy on thyroid hormones?
Thyroidectomy is the definitive management of hyperthyroidism.
Removal of the thyroid gland stops thyroid hormone production, therefore patient’s require life-long levothyroxine.
Define:
a) hypothyroidism
b) primary hypothyroidism
c) secondary hypothyroidism
a) insufficient T3 and T4
b) hypothyroidism due to thyroid pathology
c) hypothyroidism due to pathology of the pituitary gland or hypothalamus
What is the most common cause of primary hypothyroidism in the developed world?
Hashimoto’s thyroiditis
What is the most common cause of primary hypothyroidism in the developing world?
Iodine deficiency.
Prevalence is much less common in the developed world, as iodine is added to foods.
Which medications can cause primary hypothyroidism?
- amiodarone
- carbimazole
- propylthiouracil
- radioactive iodine
Pathophysiology of Hashimoto’s thyroiditis.
Autoimmune inflammation of the thyroid gland, whereby anti-TPO and anti-Tg antibodies cause destruction of the gland, and subsequently low T3 and T4 levels.
