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The Thyroid Notes

Medicine Notes > Endocrinology Notes

This is an extract of our The Thyroid document, which we sell as part of our Endocrinology Notes collection written by the top tier of University Of Leicester students.

The following is a more accessble plain text extract of the PDF sample above, taken from our Endocrinology Notes. Due to the challenges of extracting text from PDFs, it will have odd formatting:

The Thyroid Tyrosine Iodination Monoiodotyrosine Iodination Diiodotyrosine Triiodotyrosine T3 - active)

Thyroxine (T4)

Monodeiodination T3 acts via nuclear receptors to
- Increase cell metabolism o Stimulate glucose uptake and metabolism o Stimulate protein breakdown Effects are usually catabolic e.g increased BMR, heat production + O2 consumption
- Increase catecholamine effects o Vital for normal growth and development o Absence causes physical and mental retardation (cretinism) Anatomy
- The thyroid consists of two lobes connected by an isthmus
- Moves on swallowing
- Palpable in normal women
- Embriologically originates from base of tounge and descends to middle of neck
- Blood supply o Superior and inferior thyroid arteries

Hypothyroidism
- One of the most common endocrine conditions with UK prevalence of 1%
Pathophysiology
- Usually primary from underactive thyroid
- May be secondary to hypothalamic-pituitary disease (reduced TSH drive) Causes
- Autoimmune o Hashimotos thyroiditis
? Lymphocytic and plasma cell infiltration
? Goitre
? V. High antibody titres o Primary atrophic hypothyroidism
? Common
? Diffuse lymphocytic infiltration of thyroid = atrophy (no goiter)
- Acquired o Iodine deficiency o Destructive therapy (radioiodine, surgery) for cancer/hyperthyroidism o Drug induced Clinical features Symptoms Tiredness Weight gain Cold intolerance Depression Poor appetite Goitre Dry skin Constipation

Signs Mental slowless
- ataxia Deep voice Goitre Thin, dry hair Dry skin Overweight/obese Bradycardia

Investigations
- TFTs o High level serum TSH indicates primary hypothyroidism o Low free T4 confirms hypothyroid state
- FBC o Anaemia due to menorrhagia, or associated pernicious anaemia
- LFT o Increased aspartate transferase levels from muscle/liver
- Lipids o Hypercholesterolaemia
- U+E o Hyponatraemia due to increase in ADH and impaired free water clearance Management
- Replacement therapy with levothyroxine (T4) for life

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