Welcome to Phoenix Rising!
Created in 2008, Phoenix Rising is the largest and oldest forum dedicated to furthering the understanding of, and finding treatments for, complex chronic illnesses such as chronic fatigue syndrome (ME/CFS), fibromyalgia, long COVID, postural orthostatic tachycardia syndrome (POTS), mast cell activation syndrome (MCAS), and allied diseases.
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I presume this guy specialises in some way - I'd be astonished if he can cover all areas of medicine. Neurological and endocrinological stuff, it seems.
Well, that is how healthcare tends to be delivered, really. An interdisciplinary team of doctors from various specialties is what makes up a hospital.