Synopsis
Explain hormone synthesis, transport, receptor signalling, pulsatility and feedback, then use dynamic patterns to localise endocrine dysfunction without relying on isolated concentrations.
- Peptide hormones are synthesised as precursors, stored and released by exocytosis, whereas steroid hormones are synthesised from cholesterol and usually diffuse out as they are made.
- Water-soluble hormones commonly signal through surface receptors and second messengers; lipid-soluble hormones often bind intracellular receptors that alter transcription.
- Binding proteins increase total circulating hormone and buffer availability, while free hormone is usually the biologically active fraction sensed by feedback systems.
Reasoning priorities
Compare upstream drive with target-gland output.
Judge whether the trophic hormone is appropriate for the target level; reference ranges alone can hide an inappropriately normal result.
Worked reasoning
A model axis has repeatedly low target-gland free hormone and a trophic hormone concentration above its reference range, sampled under appropriate stable conditions without exogenous hormone.
- Start with the target hormone: repeated low free concentration indicates reduced circulating output rather than an isolated binding-protein change.
- Ask whether upstream drive is appropriate; the raised trophic hormone shows that feedback sensing and pituitary response are active.
- Localise the dominant dysfunction to the target gland because it fails to produce adequate hormone despite increased stimulation.
- The final pattern is primary target-gland failure, with the named gland and cause requiring axis-specific assessment.
- Verify by predicting the opposite central pattern: low target hormone with low or inappropriately normal trophic signal.