Reproductive hormone stability with prolonged intranasal oxytocin in adults with obesity

Oxytocin, a posterior pituitary hormone known for its role in parturition and lactation, is also implicated in many physiologic functions. Intranasal oxytocin is under investigation for obesity treatment, among other indications. The interplay of anterior and posterior pituitary hormones is currently not well understood. Given the well-established role of oxytocin in reproduction, it is important to examine intranasal oxytocin effects on prolactin and the hypothalamic-pituitary-gonadal (HPG) axis. Preclinical studies indicate that regulation of oxytocin, prolactin, and sex steroids in both sexes are intertwined; however, data in humans are limited, and no studies have reported the effects of prolonged oxytocin administration on prolactin or the HPG axis OBJECTIVE: To elucidate physiology and generate preliminary data regarding reproductive safety of prolonged intranasal oxytocin, we leveraged a completed trial to investigate oxytocin effects on circulating prolactin and sex steroid levels in adults with obesity.

Sixty-one adults with obesity (52% females) participated in a longitudinal randomized clinical trial data and received eight-weeks intranasal oxytocin (24 IU) four times daily or placebo. Main outcome measures were pre- and post-treatment fasting estradiol, testosterone, and prolactin; exploratory outcome measure was on-treatment menstrual cycle length.

Oxytocin vs. placebo groups did not differ for effects on prolactin or sex steroid levels (p's ≥ 0.140). On-treatment mean menstrual cycle length did not differ across groups (p = 0.234).

In our study, eight-weeks of intranasal oxytocin administration did not impact prolactin or sex steroid levels, or menstrual cycle length, providing preliminary support for reproductive safety of oxytocin-based therapeutics in adults with obesity.