Ovarian Antral Follicle Toxicity Induced by Phthalate Exposures

Endocrine-disrupting chemicals (EDCs) constitute a broad class of toxicants capable of altering hormone synthesis, transport, and receptor activity. Phthalate esters, a major subgroup of EDCs, are pervasive in consumer, industrial, and medical products and readily leach from these materials, resulting in human exposure through ingestion, inhalation, dermal absorption, and medical treatments. After absorption, phthalates undergo extensive biotransformation and distribute systemically, including to ovarian tissue and follicular fluid. Epidemiological studies consistently associate phthalate burden with diminished ovarian reserve, altered reproductive hormones, early menopause, pregnancy loss, and reproductive disorders. Notably, phthalate metabolites detected in follicular fluid correlate with reduced antral follicle count, impaired oocyte maturation, decreased fertilization rates, and poor medically assisted reproduction outcomes. Experimental evidence from mouse and bovine models supports these associations, demonstrating that phthalate exposure reduces antral follicle counts, disrupts steroidogenesis, causes oxidative stress, and promotes apoptosis. In vitro and mechanistic studies show that phthalates impair follicular function and hormone biosynthesis by disrupting lipid metabolism, mitochondrial function, microRNA expression, and pathways governing redox balance, inflammation, cell cycle and apoptosis. These disruptions contribute to impaired folliculogenesis, increased follicular atresia, ovulation deficits, and compromised oocyte competence. Although substantial descriptive evidence exists, significant mechanistic gaps still remain, highlighting the need for research using biologically relevant phthalate doses and approaches capable of distinguishing effects of individual congeners from mixtures.