Effect of oral melatonin administration on sex hormone, prolactin, and thyroid hormone concentrations in adult dogs

J Am Vet Med Assoc. 1999 Oct 15;215(8):1111-5.

Abstract

Objective: To determine the effect of oral melatonin (MT) administration on serum concentrations of sex hormones, prolactin, and thyroxine in dogs.

Design: Prospective study.

Animals: 8 male and 8 female adult sexually intact dogs.

Procedure: 5 male and 5 female dogs were treated with MT (1.0 to 1.3 mg/kg [0.45 to 0.59 mg/lb] of body weight), PO, every 12 hours for 28 days; the other 6 dogs were used as controls. Blood samples were collected on days 0, 14, and 28, and serum concentrations of estradiol-17 beta, progesterone, testosterone, androstenedione, 17-hydroxyprogesterone (17-HP), dihydroepiandrostenedione sulfate (DHEAS), prolactin, and thyroxine were determined. On day 5, serum MT concentrations were measured before and periodically for up to 8 hours after MT administration in 4 treated dogs.

Results: Female dogs treated with MT had significant decreases in serum estradiol, testosterone, and DHEAS concentrations between days 0 and 28. Male dogs treated with MT had significant decreases in serum estradiol and 17-HP concentrations between days 0 and 28. Serum MT concentrations increased significantly after MT administration and remained high for at least 8 hours. Prolactin and thyroxine concentrations were unaffected by treatment.

Conclusions and clinical relevance: Melatonin is well absorbed following oral administration and may alter serum sex hormone concentrations.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 17-alpha-Hydroxyprogesterone / blood
  • Absorption
  • Administration, Oral
  • Animals
  • Dehydroepiandrosterone / blood
  • Dogs / blood*
  • Dogs / growth & development
  • Estradiol / blood
  • Female
  • Gonadal Steroid Hormones / blood*
  • Hair / drug effects
  • Hair / growth & development
  • Male
  • Melatonin / administration & dosage
  • Melatonin / blood
  • Melatonin / pharmacology*
  • Prolactin / blood*
  • Prospective Studies
  • Testosterone / blood
  • Thyroxine / blood*

Substances

  • Gonadal Steroid Hormones
  • Testosterone
  • Dehydroepiandrosterone
  • Estradiol
  • 17-alpha-Hydroxyprogesterone
  • Prolactin
  • Melatonin
  • Thyroxine