( Estrogen ( ( can ( ( ( weaken ( the ( vein walls ) ) ) , ) ( leading ( to ( ( the changes ) ( that ( cause varicosities ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Estrogen)) (VP (MD can) (VP (VB weaken) (NP (DT the) (NN vein) (NNS walls)) (, ,) (S (VP (VBG leading) (PP (TO to) (NP (NP (DT the) (NNS changes)) (SBAR (WHNP (WDT that)) (S (VP (VBP cause) (NP (NNS varicosities))))))))))) (. .)))
Estrogen can weaken the vein walls, leading to the changes that cause varicosities.
(ROOT (S (NP (NNP Estrogen)) (VP (VBZ causes) (NP (NP (DT the) (NNS changes)) (PP (IN of) (NP (NN puberty))))) (. .)))