letter on iodine and evolution of stomach and thyroid

Sebastiano Venturi venturis at nf.infotel.it
Fri Sep 25 10:16:38 EST 1998


Might iodide have in Gastric Mucosa an ancient antioxidant role ?   Why
the primitive Thyroxine
(T4)  is transformed in Triiodothyroxine (T3), the real active hormone
of modern Vertebrates ?

Dear sir :
   the thyroid gland is, embryogenetically and phylogenetically, derived
from primitive gut , and we
may consider the thyroid cells such as primitive gastroenteric cells,
which , during evolution , are
migrated and specialized in intake of iodides, and in storage and
elaboration of iodine compounds.
Stomach and  thyroid share iodine-concentranting ability  and many
morphological and functional
similarities such as apical microvilli , secretion of glycoproteins
(thyroglobulin and mucin) and
amino-acid hormones, the digesting and readsorbing ability and lastly,
similar ability to form
iodotyrosines by peroxidase activity (1). But gastric iodide-pump,
phylogenetically more primitive
than the thyroidal one, has lower affinity for iodide and not  respond
to, more recent, TSH.
      Which is the role of iodide in physiopathology of the stomach?
Iodides reduce, by peroxidase, the oxygen of H2O2  in  normal thyroid
hormonogenesis and , are able
to defend cells from lipid peroxidation in rats (2). In previous work
(3), we have reported  that
iodine-deficiency (or excess) might constitute a risk factor for gastric
cancer and atrophic gastritis
both by regulating gastric trophism  and by antagonizing ( in thyroid
and in gastric mucosa ) the
action of those iodine-inhibitors such as nitrates, thiocyanates and
salt , well-known  risk-factors for
gastric carcinogegesis.    Recently (4) , we have hypothesized  that
iodide might have a 
( phylogenetically  primitive) antioxidant role  in more ancient organs
, particularly in  the stomach.
In fact , three billion years ago, Algae, which contain the highest
level of iodine, were the first living
cells to produce oxygen, toxic at that time, in terrestrial atmosphere .
So, algae cells required a
protective antioxidant action , in which iodides might have a specific
role. 
       The thyroid gland is, phylogenetically , a modern organ , and its
function started and was
improved from primitive  Chordates to more recent Mammalia . Recent are
the T3-nuclear-receptors
in comparison with primitive T4 . In fact thyroxine is present in
fibrous exoskeletal tissues of the
lowest animals ( Invertebrates ) without any hormonal action .   
       When the primitive marine-animals started to emerge from the sea
, rich of iodine, and 
transfered in iodine-deficient mainland, its terrestrial diet became
deficient of iodine and rich of
iodine-competitors ( nitrates, nitrites, thiocyanates, some glycosides,
etc.) .
 So, we believe that  these animals learned  to use the
not-competitivized  T4 , to transport into the
cells antioxidant-iodide , utilizing the remaining T3 for metamorphosis
and thermogenesis , with a
new hormonal action by formation of the modern  T3-receptors .

    Yours sincerely 
                                                                                         
Sebastiano Venturi  &  Marta Venturi 
                                                                                                
via  Tre  Genghe, 2
                                                                                         
Servizio di Igiene e Sanità Pubblica
                                                                                          
USL n.1 - Reg. Marche
                                                                                         
61016 - PENNABILLI   (Italy)
							   E-Mail: venturis at nf.infotel.it

       REFERENCES				

1) Banerjee RK, Bose AK, Chakraborty TK,et al. (1985)
Peroxidase-catalysed iodotyrosine formation
    in dispersed cells of mouse extrathyroidal tissues. J Endocrinol
,106:2, 159-65
2) Katamine S, Hoshino N, Totsuka K, Suzuki M (1985) Effects of the
long-term feeding of  
     high-iodine eggs on lipid metabolism and thyroid function in rats.
J Nutr Sci Vitaminol 31:339-53
3) Venturi S, Venturi A, Cimini D, Arduini C, Venturi M, Guidi A (1993)
A new hypothesis: iodine 
    and gastric cancer. Europ J Cancer Prevention 2:17-23
4) Venturi S, Guidi A, Venturi M (1996) I disordini extra-tiroidei da
carenza iodica. Qual é il reale 
    fabbisogno di iodio ? Le Basi Razionali della Terapia. 16: 267-75




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