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  • Created by: jo bill
  • Created on: 20-12-14 12:19

hormones of the thyroid

TRH  -  thyrotropin-releasing hormone TSH  -  thyroid stimulating hormone MIT   -  monoiodotyrosine DIT   -  diiodotyrosine T3     -  triiodothyronine T4     -  thyroxine (tetraiodothyronine) TG    -  Tg,  thyroglobulin TBG  -  thyroid binding globulin D1-D3   deiodinases TR     -  THR, thyroid receptor RXR  -  retinoid X receptor (coregulator) thyroid : composed of follicles 

  • thyroid hormones synthesised by iodination of tyrosine on thyroglobulin

actions of thryroid hormones

  • T3 is much more potent than T4, largely because T4 needs to be converted to T3 for activity at target cells
  • increase BMR - increase oxygen consumption, energy expenditure, heat production
  • increase turnover of metabolic fuels
  • increase food intake
  • increase responsiveness to catecholamines eg. tachcardia
  • essential for growth, development and maintainance of neural integrity

thyroid disease  Hypothyroidism

  • decreased activity
  • iodine deficieny (simple goitre) - gland enlargement
  • severe forms: cretinism in children, myxoedema in adults
  • later stages of hashimotos thyroiditis (autoimmune)
  • symptoms- decreased activity, tired, feel cold, slow mentally, decreased CO, weight gain, hair thinning/loss
  • treatment - thyroxine sodium 25-200ug

Hyperthyroidism (Graves disease, thyrotoxicosis)

  • increased activity
  • mostly due to production of antibodies that stimulate excess secretion T3/T4
  • may cause modest goitre 
  • early stages of Hashimotos thyroiditis (autoimmune)
  • symptoms- increased activity, exopthalmos, weight loss despite increased appetite, palpitations, tremor, cold tolerance, muscle weakness, sweating
  • treatment - carbimazole 15-40 mg, propylthiouracil 50mg, radioactive iodine 131 mg, partial thyroidectomy

Adrenal glands structure

  • cortex - mineralcorticoid (aldosterone), glucocorticoids (cortisol)
  • medulla- catecholamines (adrenaline, noradrenaline
  • CNS -> CRH -> ACTH -> adrenal -> Glucocorticoids/mineralcorticoids -> Biological effects


  • zona reticullaris - mainly androgens(DHEA)
  • zona fasciculata - glucocorticoids (cortisol)
  • zona glomerulosa - mineralcorticoid (aldosterone)


  • mineralcorticoid
  • secretion stimulated by:-

decrease ECF vol and/or decrease BP - stretch receptors in atria
decrease ECF osmolarity - direct effect on adrenal increase K+ conc - direct effect on adrenal increase Angiotensin II

  • acts on the idney distal cortical principal cells

increase Na+ retention - via ENaC and Na-K ATPase                                                        …


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