( ( ( The symptoms ) ( of menopause ) ) ( ( are ( caused ( by ( ( the changes ) ( in ( estrogen levels ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NNS symptoms)) (PP (IN of) (NP (NN menopause)))) (VP (VBP are) (VP (VBN caused) (PP (IN by) (NP (NP (DT the) (NNS changes)) (PP (IN in) (NP (NN estrogen) (NNS levels))))))) (. .)))
The symptoms of menopause are caused by the changes in estrogen levels.
(ROOT (S (NP (NNP Estrogen)) (VP (VBZ causes) (NP (NP (DT the) (NNS changes)) (PP (IN of) (NP (NN puberty))))) (. .)))