Hypothyroidism hippocampus

Clos, J. and Legrand, C. (1990) An interaction between thyroid hormone and nerve growth factor promotes the development of hippocampus, olfactory bulbs and cerebellum a comparative biochemical study of normal and hypothyroid rats. Growth Factors 3 205-220. 

Hypothyroidism appears to produce relatively severe effects on the volumetric, longitudinal and areal growth of the hippocampus in contrast to the forebrain where such effects are smaller. Thus there is a desynchronization of coordinated growth between these two brain regions (Rabie et al., 1979). Such a mismatch could lead to miswiring of connecting circuitry and/or behavioral deficits. 

Calcineurin reduces postsynaptic activity [271], blocks LTP [272], induces and maintains LTD [273], and impairs hippocampus-dependent memory formation in mice [274]. It indirectly activates protein phosphatase 1 (PPl) by inactivating its natural inhibitor inhibitor 1 [275], thus enabling PPl to dephosphorylate many molecules including P-CaMKII [271,276]. During hypothyroidism, calcineurin activity and basal protein levels are increased in CAl area of the hippocampus [1, 229, 265]. This increase is normalized in nicotine treated hypothyroid rats [22]. It is likely that the increase in the activity and levels of calcineurin in hypothyroid rats may account for the reduced CaMKII activity and consequent impairment of short-term memory and LTP. By normalizing activity and levels of calcineurin in hypothyroid rats, nicotine may have prevented impairment of LTP during hypothyroidism. 

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