Testosterone & infant feeding

Accompanying client resource

Testosterone & Bodyfeeding  

“If a transgender man is chestfeeding/breastfeeding (or pumping and feeding the child that milk), the provider should help them evaluate the possible risks to the child against the benefit of testosterone to the patient. Ruling out taking testosterone while nursing, regardless of the benefit to the parent, is an approach that implicitly values an unknown and possibly small effect on the child [Glaser et al., 2009] over a known significant benefit for the parent. These relative risks and benefits as well as the medical uncertainty around these decisions should be presented to and discussed with patients with an eye towards global harm reduction” [1, p. 16, emphasis ours].

Testosterone is taken by some transgender, Two-Spirit A term used within some Indigenous communities to reflect complex Indigenous understandings of gender and sexuality and the long history of sexual and gender diversity in Indigenous cultures. Two-Spirit encompasses sexual, gender, cultural and spiritual identity. It may refer to cross-gender, multi-gender or non-binary gender roles, non-heterosexual identities, and a range of cultural identities, roles and practices embodied by Two-Spirit peoples. Some people also use "2-Spirit" or "2S." (Source: Battered Women’s Support Services) , or non-binary Umbrella term referring to people whose gender does not fall within the binary gender system of woman/girl or man/boy. Some individuals identify as non-binary while others may use terms such as gender non-conforming, genderqueer, or agender. Non-binary people may or may not conform to societal expectations for their gender expression and gender role, and they may or may not seek gender-affirming medical or surgical care. (TTNB) people to affirm their gender. When bodyfeeding an infant, testosterone may decrease feelings of dysphoria and may prolong the feeding relationship [2,3]. However, there is little research into how this may impact milk supply or milk transfer of testosterone to an infant [3].  

Parents may choose to take testosterone while bodyfeeding to affirm their gender, to reduce estrogen-related features, induce testosterone-related features, and/or decrease gender dysphoria Distress resulting from a difference between a person’s gender and their sex assigned at birth, associated gender role, and/or primary and secondary sex characteristics. (Source: WPATH) [2,3]. 

A case study by Glaser et al. [4] investigated testosterone therapy in a lactating cisgender Refers to people who are non-trans, i.e. whose gender matches their assigned sex at birth. woman who was experiencing depression, anxiety, memory loss, and fatigue in the postpartum period. Researchers measured testosterone levels in the blood serum and milk when the participant took testosterone sublingually, vaginally, and subcutaneously as a pellet implant. While they found detectable levels in her blood, there was no significant increase of testosterone in her milk. The male infant showed no physical signs of excessive testosterone and the infant’s blood levels of testosterone measured low at baseline and remained low throughout the seven months of treatment. The authors concluded that testosterone therapy is safe in lactating parents. While these findings are promising, they are limited by a case study of one and did not report on the participant’s milk supply while taking testosterone.  

In a qualitative study of transmasculine Refers to trans people who were assigned female at birth and whose gender expression leans towards the masculine. individuals’ experiences with lactation by MacDonald et al. [2], one participant reported taking testosterone while bodyfeeding to manage feelings of dysphoria. The participant began taking the “standard dose of female-to-male” testosterone when his infant was 21 months old with the guidance of a pediatrician and endocrinologist A doctor specially trained in the study of hormones and their actions and disorders in the body. . He shared that he watched his child closely for “signs of early puberty such as body hair” and, after 15 months of testosterone therapy, the child had normal levels of testosterone in their blood. This participant did not notice a change in milk supply when he started testosterone. Starting testosterone, along with light chest binding Wearing compression garments or using other methods to flatten the chest. , affirmed his gender and allowed him to postpone chest construction A gender-affirming, upper surgery that removes breast tissue and sculpts remaining tissue into a shape that is typically considered to be more masculine. surgery until after his child naturally weaned.

A case study by Oberhelman-Eaton et al. [3] details how a transgender man started gender-affirming testosterone therapy at 13 months postpartum while bodyfeeding his infant. Testosterone was administered subcutaneously weekly, and blood samples were collected at baseline, 4 days after testosterone was started, and again at 14, 28, 70, and 134 days, measured just prior to the next subcutaneous administration. Milk and infant serum testosterone levels were also measured, and the infant was monitored by their pediatrician for signs of virilization. While parental serum and milk levels of testosterone rose, serum testosterone levels in the infant remained undetectable. The infant fed for another 137 days until they self-weaned, and the parent did not detect any changes in milk supply or feeding patterns.

See original article for more information regarding dosage and testosterone levels: Initiation of Gender-Affirming Testosterone Therapy in a Lactating Transgender Man.  

The limited research we have on testosterone and infant feeding is based on healthy, full-term infants. Implications for preterm infants are not considered in this content.

When discussing taking testosterone while bodyfeeding, providers should review other gender-affirming strategies that may decrease gender incongruence A mismatch between a person's gender and the sex they were assigned at birth. or dysphoria. These include lightly binding Wearing compression garments or using other methods to flatten the chest. the chest, wearing affirming clothing, meeting with other TTNB parents (online or in-person), and accessing mental health supports.

Informed consent and informed decision making require clinicians to balance the needs of the client, their infant, and the available evidence. While the evidence that we do have is scant, when we consider the pharmacokinetics of testosterone, the positive impact of gender-affirming hormones, and the benefits of bodyfeeding, the benefits of taking testosterone while bodyfeeding may outweigh the risks for some clients.

Transfer of testosterone in human milk

Testosterone and milk supply  

Testosterone may block prolactin, a hormone involved in establishing and maintaining milk production [6]. While ongoing milk production is thought to be more strongly associated with milk removal than prolactin release [7], testosterone may decrease milk production if taken while bodyfeeding. This risk may increase if taken earlier in the postpartum period. Milk supply was not measured in any of the included case studies [2–4].  

Transdermal testosterone

Parents using transdermal testosterone should follow directions carefully to avoid accidental transfer to the infant through skin-to-skin contact.  

1. Hoffkling A, Obedin-Maliver J, Sevelius J. From erasure to opportunity: A qualitative study of the experiences of transgender men around pregnancy and recommendations for providers. BMC Pregnancy Childbirth. 2017;17: 332. doi:10.1186/s12884-017-1491-5
2. MacDonald T, Noel-Weiss J, West D, Walks M, Biener M, Kibbe A, et al. Transmasculine Refers to trans people who were assigned female at birth and whose gender expression leans towards the masculine. individuals’ experiences with lactation, chestfeeding, and gender identity A person's deeply held, internal sense of themself as male, female, a blend of both or neither. (Source: GenderSpectrum.org) : A qualitative study. BMC Pregnancy & Childbirth. 2016;16: 1–17. doi:10.1186/s12884-016-0907-y
3. Oberhelman-Eaton S, Chang A, Gonzalez C, Braith A, Singh RJ, Lteif A. Initiation of gender-affirming testosterone therapy in a lactating transgender man. J Hum Lact. 2022;38: 339–343. doi:10.1177/08903344211037646
4. Glaser RL, Newman M, Parsons M, Zava D, Glaser-Garbrick D. Safety of maternal testosterone therapy during breast feeding. Int J Pharm Compd. 2009;13: 314–317.  
5. Verstegen RHJ, Anderson PO, Ito S. Infant drug exposure via breast milk. Brit J Clinical Pharma. 2022;88: 4311–4327. doi:10.1111/bcp.14538
6. Drugs and Lactation Database (LactMed®). Testosterone. National Institute of Child Health and Human Development. 2022.
7. Grzeskowiak LE, Wlodek ME, Geddes DT. What evidence do we have for pharmaceutical galactagogues in the treatment of lactation insufficiency? A narrative review. Nutrients. 2019;11: 1–21. doi:10.3390/nu11050974