Draft Deliberative – Do NOT Cite, Quote, or Distribute State of the Science: Nonmonotonic Dose Responses V7 State of the Science Evaluation: Nonmonotonic Dose Responses as They Apply to Estrogen, Androgen, and Thyroid Pathways and EPA Testing and Assessment Procedures U.S. Environmental Protection Agency Jointly developed by: Office of Research and Development Office of Science Policy National Health and Environmental Effects Research Laboratory National Center for Environmental Assessment National Center for Computational Toxicology Office of Chemical Safety and Pollution Prevention Office of Pesticide Programs Office of Pollution Prevention and Toxics Office of Science Coordination and Policy June 2013 1 | Page Draft Deliberative – Do NOT Cite, Quote, or Distribute State of the Science: Nonmonotonic Dose Responses V7 Table of Contents Foreward ................................................................................................................................................. 9 Executive Summary ............................................................................................................................... 10 1. Introduction .................................................................................................................................. 20 1.1 Background ............................................................................................................................ 21 1.2 Scope of the Current Evaluation ............................................................................................. 27 1.3 Central Scientific Questions .................................................................................................... 28 2. General Biological Concepts and Statistical Considerations for NMDR ............................................ 28 2.1 Pharmacokinetic Processes .................................................................................................... 28 2.2 Modes of Action and Adverse Outcome Pathways.................................................................. 29 2.3 Determinants of Nonmonotonic Dose-Response .................................................................... 31 2.4 The Hypothalamic-pituitary-gonadal and Hypothalamic-pituitary-thyroid Axes ...................... 34 2.5 Statistical Issues and Experimental Design .............................................................................. 40 3. NMDRs from in vitro Studies .......................................................................................................... 42 4. NMDRs from in vivo Studies ........................................................................................................... 55 4.1 Aquatic Models ...................................................................................................................... 55 4.1.1 Literature Search and Analysis, Aquatic Species ............................................................ 56 4.1.2 NMDRs in the Estrogen Hormone System in Aquatic Species ........................................ 62 4.1.2.1 Estrogen Receptor Agonists ........................................................................................ 62 4.1.2.2 Selective Estrogen Receptor Modulator (Tamoxifen) .................................................. 64 4.1.3 NMDRs in the Androgen Hormone Pathway in Aquatic Species .................................... 64 4.1.3.1 Androgens .................................................................................................................. 64 4.1.3.2 Androgen Receptor Antagonists ................................................................................. 69 4.1.3.3 Steroid Synthesis Inhibitors......................................................................................... 70 4.1.3.4 Role of Compensatory Processes in NMDR – Examples from Fish Time-Course Studies with Three EDCs ........................................................................................................................ 73 4.1.4 NMDRs in the Thyroid Hormone Pathway in Aquatic Species ........................................ 79 4.1.4.1 Fish ............................................................................................................................. 79 4.1.4.2 Amphibians ................................................................................................................ 82 4.2 Mammalian Models ............................................................................................................... 83 4.2.1 Literature Search and Selection Strategy for E and A Pathways ..................................... 83 4.2.1.1 Specific Considerations in Reviewing the Literature on E and A ................................... 85 4.2.2 Estrogen Hormone System ........................................................................................... 92 4.2.2.1 Ethinyl Estradiol (EE2) [A.1.a] ...................................................................................... 94 4.2.2.2 17β Estradiol (E2) [A.1.b] ............................................................................................ 96 4.2.2.3 Diethylstilbestrol (DES) [A.1.c] .................................................................................... 96 4.2.2.4 Genistein [A.1.d] ......................................................................................................... 97 4.2.2.5 Bisphenol A [A.1.k] ..................................................................................................... 99 4.2.2.6 Selective Estrogen Receptor Modulators (SERMs) [A.2]............................................. 101 4.2.2.7 Tamoxifen [A.2.b] ..................................................................................................... 101 4.2.2.8 Aromatase Inhibitors (AI: block androgen to estrogen synthesis) [A.3] ...................... 102 4.2.2.9 Exemestane [A.3.b] ................................................................................................... 102 4.2.3 Androgen Hormone System [B] .................................................................................. 102 4.2.3.1 Vinclozolin [B.1.b] ..................................................................................................... 106 4.2.3.2 Procymidone [B.1.c].................................................................................................. 106 4.2.3.3 Phthalates [B.2] ........................................................................................................ 107 4.2.3.4 Semicarbazide [B.4] .................................................................................................. 115 4.2.3.5 Multiple Molecular Initiating Events [B.5] ................................................................. 115 2 | Page Draft Deliberative – Do NOT Cite, Quote, or Distribute State of the Science: Nonmonotonic Dose Responses V7 4.2.3.6 Androgen Receptor Agonists [B.6] ............................................................................ 116 4.2.3.7 Selective Androgen Receptor Modulators (SARMS) [B.7] .......................................... 118 4.2.4 Thyroid ....................................................................................................................... 119 4.2.4.1 Environmental Contaminants and Thyroid Disruption ............................................... 120 4.2.4.2 Literature Search and Analysis .................................................................................. 121 4.2.4.3 Review of Three Major Targets for Nonmonotonic Thyroid Pathway Disruption ....... 122 4.2.4.4 Results of Literature Analysis .................................................................................... 129 4.2.4.5 Conclusions for Thyroid Studies ................................................................................ 133 4.3 Human Studies and Epidemiology ........................................................................................ 136 4.3.1 Context for Human Studies in this Review .................................................................. 136 4.3.2 Interpreting Epidemiological Evidence ........................................................................ 136 4.3.2.1 Multiple Exposures (Combined or in Sequence) ........................................................ 137 4.3.2.2 Exposure Assessment ............................................................................................... 137 4.3.3 Moving Forward – Converging Evidence ..................................................................... 138 4.3.4 Summary .................................................................................................................... 139 5. Conclusions ................................................................................................................................. 139 5.1 General Conclusions ............................................................................................................. 139 5.1.1 Overall Conclusions: Estrogen, Androgen, and Thyroid ............................................... 142 5.2 Central Scientific Questions and Answers ............................................................................. 144 5.2.1 Do nonmonotonic dose responses (NMDRs) exist for chemicals and if so under what conditions do they occur? .......................................................................................... 144 5.2.2 Do NMDRs capture adverse effects that are not captured using our current chemical testing strategies (i.e., false negatives)?.....................................................................