( ( According ( to ( western medicine ) ) ) ( , ( ( ( the symptoms ) ( of menopause ) ) ( ( are ( caused ( by ( changes ( in ( estrogen levels ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (VBG According) (PP (TO to) (NP (JJ western) (NN medicine)))) (, ,) (NP (NP (DT the) (NNS symptoms)) (PP (IN of) (NP (NN menopause)))) (VP (VBP are) (VP (VBN caused) (PP (IN by) (NP (NP (NNS changes)) (PP (IN in) (NP (NN estrogen) (NNS levels))))))) (. .)))
According to western medicine, the symptoms of menopause are caused by changes in estrogen levels.
(ROOT (S (NP (NNP Estrogen)) (VP (VBZ causes) (NP (NP (DT the) (NNS changes)) (PP (IN of) (NP (NN puberty))))) (. .)))