Aim: Androgen excess predisposes the organism to develop metabolic-endocrine and reproductive dysfunctions, among them the development of a phenotype resembling that ofhumanPolycystic Ovary Syndrome(PCOS).<u>METHODS</u>: We analyzed the impact of a single neonatal (5day-old)testosterone propionate(TP; s.c. 1.25mg/female pup) dose on: a) several metabolic-endocrine activities and b) ovarian steroidogenic and granulosacell(GC) functions and also follicular population in juvenile and adult TP and control (CT)rats. <u>Key Findings</u>: Compared to CTrats, TPanimalswere characterized by: a) acceleratedgrowth, hyperadiposity and hyperleptinemia, b) very early (pre-weaning age) vaginal opening, c)hyperinsulinemiain adult life, d) dysfunctional ovariansteroidogenesis, e) conserved GC functionality in both juveniles (in vitro) and adults (in vivo), and f)estrous cyclesarrested atestrus. Finally, histological studies of the ovaries indicated that in TP (vs. CT)rats: i) primary and antral follicle frequencies were 3- and 15-fold higher and lower, respectively, in juveniles and ii) secondary and atretic follicle frequencies were 3- and 5-fold lower and higher, respectively, in adults. Large cystic images without corpus luteum were observed in the ovaries from adult TPratsonly. <u>Significance</u>: Our results strongly suggest that transient neonatal hyperandrogenemia induced early misprogramming of metabolic-endocrine and ovarian (steroidogenesis/folliculogenesis) functions. Conversely, TPratspreserved their ovary GC endocrine function. Our results further support the high risk of developingovarian hyperstimulation syndromeforinfertilewomen with transient/chronic hyperandrogenemia (PCOS) subjected to assisted reproductive technologies.