Thyroid Disfunction Flashcards
What negative feedback loops occur with T4 (thyroxine)
T4 is released by the follicular cells in the thyroid glands when stimulated by TSH, thyroid stimulating hormone. TSH is released from the anterior pituitary when stimulated by TRH, thyrotrophin releasing hormone, via the hypophyseal portal system.
T4 inhibits release of both TSH and TRH, a classic negative feedback loop.
What deficiency causes hypothyroidism, and where is it most commonly found?
Iodine deficiency causes hypothyroidism, found most often far away from the sea, landlocked countries etc.
What is the treatment for hypothyroidism?
Why must care be taken with administering treatment?
How long does treatment take?
Thyroxine replacement therapy, Levothyroxine (T4) for life. Starting dose depends on severity. Increases blood pressure so caution required with elderly and with heart disease. Normalisation of blood tests takes 6-8 weeks.
High TSH suggests under-replacement
Low TSH suggest over-replacement
What symptoms or signs of hyperthyroidism?
Goitre (more common in women)
Lid retraction (exophthalmos/ proptosis)
Lid lag
Losing weight
Tachycardia
Arrhythmia
Warm Peripheries
Muscle ache
Insomnia
Diarrhoea
Restlessness
Three causes of hyperthyroidism
Graves disease (most common)
Thyroiditis
Nodular thyroid disease
Mechanism for graves’ disease
Autoimmune mediated stimulation of TSH receptor. Stimulates hormone synthesis of T4
Treatment of hyperthyroidism
Medication:
Carbimazole or Propylthiouracil,
beta blockers for symptoms
Surgery:
If patient preference
Radioactive Iodine:
Good definitive non-surgical option.
Hyperthyroidism in pregnancy
In graves disease the antibodies can cross the placenta, meaning the baby can be born with hyperthyroidism.
4 types of Goitre
Diffuse goitre
Thyroiditis or auto immune thyroid disease
Nodular goitre
Fibrotic goitre
Iodine deficinecy
