3.3: Sex Hormones

The Psychology of Women - An Inclusive Approach · LibreTexts

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    When you hear the phrase "sex hormones," you might assume that boys have testosterone and girls have estrogen. This characterization ignores biology. Everyone’s body produces both testosterone and estrogen, but bodies differ in both the relative levels and how the body responds to hormone messages. Estrogen is actually the term for a group of hormones, the most common of which is estradiol. Testosterone, on the other hand, is one hormone in a group referred to as androgens. Estrogens are typically higher in people with ovaries, and androgens are typically higher in people with testes, but both are circulating in everyone (Hines, 2020). The idea that these hormones belong to one sex contributes to the misconception that male and female bodies are fundamentally different and erases the way everyone’s body comes from a largely shared biological foundation. Recall that humans have 46 chromosomes, only two of those determine biological sex, the other 44 are autosomes. And even within the sex chromosomes, sexual differentiation begins with just one gene, SRY, which sets the rest of the process in motion.

    The way that gender-affirming hormone therapy works illustrates this point really well. Transmasculine people who take testosterone develop deeper voices, increased body hair, and a typically male redistribution of body fat, while transfeminine people who take estrogen develop breast tissue, softer skin, and a typically female redistribution of body fat (Coleman et al., 2022). The same hormones produce the same effects regardless of the person's sex assigned at birth because our underlying biology responds to hormone signals, not chromosomes.

    Organizing vs. Activating Effects

    One of the most important distinctions in understanding how sex hormones shape development is between organizing effects and activating effects (Phoenix et al., 1959). Organizing effects occur during prenatal development and produce lasting structural changes to the body and brain. For example, prenatal testosterone exposure triggers the development of male-typical reproductive anatomy (which we will cover in detail in Section 3.3). These changes are largely permanent.

    Activating effects, by contrast, occur throughout life and depend on the current presence of hormones. For example, the increase in testosterone during puberty increases muscle mass and triggers sperm production, but both decrease if testosterone levels drop. Additionally, estrogens and other hormones can initiate and direct the menstrual cycle in puberty, which responds to cyclical hormone levels and will cease during pregnancy and at menopause.

    The distinction between organizing and activating effects is useful, but it is not as straightforward as it first appears. Puberty, for instance, involves both. The structural changes of puberty (voice deepening in people with testes, changes in bone structure) are organizing effects, while things like sex drive and mood fluctuations tied to menstrual cycles are activating effects. In Section 3.4 we will discuss how puberty is increasingly recognized as a second organizing period, not just an activating one (Schulz et al., 2009). This means the developing adolescent brain is being shaped by hormones in lasting ways, not just temporarily activated by them. In section 3.5 we will discuss the importance of this for gender diverse youth.

    Section Key Terms

    This page titled 3.3: Sex Hormones was last modified on Fri, 11 Sep 2026 19:00:58 GMT and is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Rochelle Burnaford.