[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

t-rex gout

Dear list:
I am a physician who is a long- time reader but first-time contributer.  Although I possess no knowledge of non-huiman metabolism and illnesses, I do know something about gout in our own species which may be applicable to dinosaurs.  Gout is caused by a high uric acid level which is a product of purine degredation, produced chiefly by the liver and small intestine.  At high concentrations, uric acid in the plasma can become supersaturated and can precipitate as urate crystal  in the joints leading to an acute gouty arthritis.   Up to 13% of adults have elevated uric acid levels, whereas only 2% of them ever develop gout.  The higher the uric acid level the more likely gout will develop.
     High uric acid levels can be caused by over-production or under excretion.  There are a number of illnesses associated with over-production, the most common being idiopathic (unknown).  In dinosaurs I think some potentially relevant uric acid elevaters would be: exercise, rhabdomyolysis (severe muscle trauma leading to degredation of skeletal muscle ATP), obesity (quite unlikely), and a purine-rich diet.  Such foods in humans include organ meats (liver, kidney, sweatbreads), and anchovies.  Underexcretion of uric acid is a more common cause of gout and causes include a number of illnesses including the potentially important-for-dinosaurs: starvation.  Again, the majority of cases have an idiopathic cause.  Reproductive hormones seem to protect females; their uric acid levels begin to rise only after menopause.
     Most first attacks of gouty arthritis follow 20-40 years of sustained elevated uric acid levels, and the first attack is explosive and intensely painful.  The arthritis is initially monoarticular, in the lower extremities (usually the first metatarsal-phalangeal joint), and subsides in 7-10 days.  Some individuals have only one episode of acute arthritis, others develop recurrences.  Chronic gout is characterized by persistant polyarticular low-grade pain, evidenced by destruction of bone and cartilage and is associated with x-ray changes.
     I suspect after millions of years of carnivorous diets, T-rex would be well-adapted to a high-purine diet, and since it would take years of chronically high uric acid levels to produce the changes seen in fossils, a dietary cause for a T-rex's gout seems unlikely to me.  I suspect that there was a large genetic variability in uric acid production/excretion in dinosaurs, and that those on the high end of the scale would be predisposed to gout.  If their metabolism is similar to humans, I would expect a T-rex with gout to be male and an older individual.  As an aside, humans have increased levels of uric acid compared to prosimians and other lower primates.  Uric acid is a very powerful antioxident, on the level of vitamin C, and it has been proposed that it may contribute to human's longer life span although this has no supporting evidence at present.      Ken Clay,M.D.