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  <head>
    <title>023-01 Foundations</title>
    <ownerName>Integrated Medical Foundations</ownerName>
  </head>
  <body>
    <outline text="Hypothalamic-pituitary control and endocrine feedback">
      <outline text="Hormones, classes, and binding">
        <outline text="Level reflects secretion, binding, metabolism, clearance">
          <outline text="Not gland activity alone"/>
        </outline>
        <outline text="Peptides: precursors, vesicles, exocytosis">
          <outline text="Membrane receptors and second messengers"/>
        </outline>
        <outline text="Steroids: from cholesterol, made on demand">
          <outline text="Protein-bound, intracellular receptors, transcription"/>
        </outline>
        <outline text="Thyroid hormones act through nuclear receptors"/>
        <outline text="Catecholamines act through surface receptors"/>
        <outline text="Only unbound hormone reaches tissues">
          <outline text="Binding changes alter total, not free activity"/>
          <outline text="Pregnancy, oestrogen, liver disease, protein loss"/>
        </outline>
      </outline>
      <outline text="Feedback, rhythms, and dynamic testing">
        <outline text="Releasing hormone, trophic hormone, peripheral gland"/>
        <outline text="Primary failure: low target, high trophic"/>
        <outline text="Central failure: low target, low or normal trophic"/>
        <outline text="Autonomous secretion suppresses upstream signals"/>
        <outline text="Pulsatile and circadian secretion">
          <outline text="Gonadotropin-releasing hormone must be intermittent"/>
          <outline text="Continuous exposure suppresses the axis"/>
          <outline text="Cortisol peaks near waking, falls at midnight"/>
        </outline>
        <outline text="A single value can mislead"/>
        <outline text="Suppression tests: can autonomy be restrained"/>
        <outline text="Stimulation tests: can reserve respond"/>
      </outline>
      <outline text="Hypothalamus and anterior pituitary">
        <outline text="Regulatory peptides enter portal circulation"/>
        <outline text="Releasing hormones drive trophic hormones"/>
        <outline text="Somatostatin inhibits growth and thyroid-stimulating hormones"/>
        <outline text="Dopamine tonically inhibits prolactin"/>
        <outline text="Masses secrete, compress, or both">
          <outline text="Upward: optic chiasm, temporal fields"/>
          <outline text="Lateral: ocular motor nerves, sympathetic fibres"/>
        </outline>
        <outline text="Tumour haemorrhage or infarction">
          <outline text="Headache, visual loss, ophthalmoplegia"/>
          <outline text="Acute adrenal insufficiency"/>
        </outline>
      </outline>
      <outline text="Posterior pituitary and water balance">
        <outline text="Vasopressin made in hypothalamic nuclei"/>
        <outline text="Stimuli: rising osmolality, volume depletion"/>
        <outline text="V2 receptors insert aquaporins"/>
        <outline text="Diabetes insipidus: large dilute urine volumes">
          <outline text="Hypernatraemic dehydration without water access"/>
          <outline text="Central responds to desmopressin"/>
          <outline text="Nephrogenic: correct cause, reduce solute load"/>
          <outline text="Primary polydipsia can mimic"/>
        </outline>
        <outline text="Inappropriate antidiuresis">
          <outline text="Low sodium, concentrated urine"/>
          <outline text="Rapid correction risks osmotic demyelination"/>
        </outline>
      </outline>
      <outline text="Growth hormone">
        <outline text="Linear growth via insulin-like growth factor one"/>
        <outline text="Direct lipolysis and insulin resistance"/>
        <outline text="Insulin-like growth factor one integrates secretion"/>
        <outline text="Excess: gigantism before closure, acromegaly after">
          <outline text="Glucose fails to suppress growth hormone"/>
        </outline>
        <outline text="Deficiency: poor growth, reduced lean mass">
          <outline text="Random value unhelpful, stimulation testing"/>
        </outline>
      </outline>
      <outline text="Prolactin">
        <outline text="Suckling reduces dopamine, raises prolactin"/>
        <outline text="Falling sex steroids permit lactation"/>
        <outline text="High prolactin suppresses gonadotropin-releasing hormone">
          <outline text="Infertility, sexual dysfunction, bone loss"/>
          <outline text="Galactorrhoea neither required nor specific"/>
        </outline>
        <outline text="Causes: tumour, stalk, drugs, hypothyroidism"/>
        <outline text="Repeat mild rise, check macroprolactin"/>
        <outline text="Dopamine agonists shrink prolactinomas"/>
        <outline text="Distinguish tumour from drug or stalk effect"/>
      </outline>
      <outline text="Hypopituitarism">
        <outline text="Tumours, surgery, radiation, postpartum haemorrhage"/>
        <outline text="Deficits emerge gradually, variable order"/>
        <outline text="Adrenocorticotropic deficiency immediately dangerous">
          <outline text="Aldosterone kept by renin-angiotensin system"/>
        </outline>
        <outline text="Replace cortisol before thyroid hormone">
          <outline text="Thyroid first can precipitate crisis"/>
        </outline>
      </outline>
      <outline text="Functional pituitary tumours">
        <outline text="Adrenocorticotropic tumours: pituitary cortisol excess"/>
        <outline text="Thyroid-stimulating tumours: central hyperthyroidism"/>
        <outline text="Gonadotroph tumours often non-functioning"/>
        <outline text="Surgery, drugs, radiotherapy, replacement"/>
        <outline text="Long-term surveillance for late change"/>
      </outline>
      <outline text="Investigation in practice">
        <outline text="Start from phenotype and medicines"/>
        <outline text="Measure target with controlling hormone"/>
        <outline text="Repeat surprising results"/>
        <outline text="Imaging follows biochemistry">
          <outline text="Incidental lesions do not prove secretion"/>
        </outline>
        <outline text="Urgent: vision, apoplexy, sodium, adrenal crisis"/>
      </outline>
    </outline>
  </body>
</opml>
