A crossover-crossback prospective study of dibutyl-phthalate exposure from mesalamine medications and serum reproductive hormones in men

Environ Res. 2018 Jan;160:121-131. doi: 10.1016/j.envres.2017.09.025. Epub 2017 Oct 1.


Background: Phthalates, such as dibutyl phthalate (DBP), are endocrine disruptors used in some medication coatings e.g., mesalamine to treat inflammatory bowel disease (IBD).

Objectives: Taking advantage of different mesalamine formulations with/without DBP, we assessed whether DBP from mesalamine (>1000x background) altered serum hormones.

Methods: Men (N=73) with IBD participated in a crossover-crossback prospective study and provided up to 6 serum samples (2:baseline, 2:crossover, 2:crossback). Men on non-DBP mesalamine (background) at baseline crossed-over for 4 months to DBP-mesalamine (high) and then crossed-back for 4 months to non-DBP mesalamine (B1HB2-arm) and vice versa for men on DBP-mesalamine at baseline (H1BH2-arm). We divided H1BH2-arm at the median (H1<3yrs or H1≥3yrs). We estimated crossover and crossback % changes in serum reproductive hormones using multivariable linear mixed effect models.

Results: When B1HB2-arm (26 men,134 samples) crossed-over, luteinizing hormone decreased 13.9% (95% confidence interval(CI): -23.6,-3.0) and testosterone, inhibin-B, and follicle-stimulating hormone (FSH) marginally decreased; after crossback all increased 8-14%. H1BH2-arm, H1≥3yrs (25 men,107samples) had no changes at crossover or crossback whereas in H1BH2-arm,H1<3yrs (22 men,100 samples) after crossover, inhibin-B increased 13.2% (CI: 4.2,22.9), FSH decreased 9.9% (CI: -17.9,-1.1) and after crossback, inhibin-B further increased 11.3%, and FSH marginally increased.

Conclusions: High-DBP exposure may disrupt pituitary-gonadal hormones that largely reversed after exposure removal, but only in men with no or short previous high-exposure history. Paradoxically, men with longer duration of high-DBP exposure, exposure removal did not change hormone levels, suggesting that long-term high-DBP exposure may alter the pituitary-gonadal axis and make it insensitive to exposure changes.

Keywords: Crossover study; Endocrine disruptor; Hormones; Men; Phthalate.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Anti-Inflammatory Agents, Non-Steroidal / administration & dosage
  • Cross-Over Studies
  • Dibutyl Phthalate / adverse effects*
  • Endocrine Glands / drug effects*
  • Gonadal Hormones / blood*
  • Gonadotropins, Pituitary / blood*
  • Humans
  • Male
  • Mesalamine / administration & dosage
  • Plasticizers / adverse effects*
  • Prospective Studies


  • Anti-Inflammatory Agents, Non-Steroidal
  • Gonadal Hormones
  • Gonadotropins, Pituitary
  • Plasticizers
  • Dibutyl Phthalate
  • Mesalamine