Hormonal Regulation / Endocrinology

Hormonal Regulation / Endocrinology

Our body relies on an intricate signaling network driven by hormones. These chemical messengers, secreted by endocrine glands, help regulate essential processes such as growth, metabolism, the response to stress, and reproduction. The field of endocrinology focuses on understanding these hormones and the glands that produce them.

Hormonal regulation largely depends on a small gland located at the base of the brain: the pituitary gland, also called the hypophysis. Nicknamed the “master gland” of the endocrine system, it secretes several hormones that regulate different systems of the body. Among them, the gonadotropins — FSH (follicle-stimulating hormone) and LH (luteinizing hormone) — are essential for regulating the reproductive system in both women and men. The secretion of these pituitary hormones is itself stimulated by GnRH (gonadotropin-releasing hormone), produced by the hypothalamus, another gland located in the brain. This hormonal trio — GnRH, FSH, and LH — plays a central role in the functioning of the ovaries and testes. The physiology of the pituitary is one of the research topics of Gustavo Zamberlam, who studies the regulation of gonadotropin synthesis.

Daniel Bernard’s team is interested in the molecular mechanisms governing the synthesis of pituitary hormones as well as the mechanisms of action of GnRH in the pituitary cells responsible for producing FSH and LH. This team also seeks to better understand the hypothalamic-pituitary control of thyroid hormone production. Jacques Drouin’s laboratory also focuses on the pituitary and hormonal action, particularly in the context of pituitary gland development, the specialization of its cells, and its influence on the functioning of target organs such as the ovaries, testes, and adrenal glands. Mauro Silva’s team aims to better understand the functioning of the hypothalamus. This gland plays an essential role in reproduction, and the researcher is particularly interested in how neural circuits in the brain influence the release of GnRH.

Among the hormones involved in reproductive function are steroid hormones, such as androgens and estrogens. In women, estrogens are produced in the ovaries and are involved in regulating the menstrual cycle, fertility, bone health, and even cognitive functions. Estrogens act via specific receptors found in various body tissues. When estrogens bind to these receptors, certain genes are activated. Estrogen receptors are among the research interests of André Tremblay, who studies the effects of receptor activation in the ovaries.
Contrary to popular belief, estrogens are not exclusive to women and are also produced in small amounts in men. Étienne Audet-Walsh’s research group aims to understand how sex hormones such as androgens and estrogens act in the prostate and the mammary gland. The team also studies how substances called endocrine disruptors can interfere with these hormonal actions and impair proper cellular function.

Androgens — such as testosterone — are produced in men in the testes. Jacques J. Tremblay is interested in Leydig cells, which are responsible for testosterone production in the testes. An imbalance in the production of this hormone, or other steroid hormones, can be linked to several human diseases, such as certain cancers, polycystic ovary syndrome (PCOS), endometriosis, and inflammatory or autoimmune diseases. Robert S. Viger’s team studies how hormone expression and action are regulated in the ovaries and testes.

Reproductive function regulation does not rely solely on sex hormones. Other molecules also indirectly influence reproduction. For example, adipose tissue and muscles also produce hormones — known as adipokines, myokines, and irisin (the “exercise hormone”). Christopher Price’s team is interested in these long-overlooked substances, now recognized for their role in modulating ovarian function.

The hormonal system interacts with the renin-angiotensin system, a key regulator of blood pressure. When this system becomes overactive — for example, due to excessive production of angiotensinogen and renin — it can contribute to the development of preeclampsia, a pregnancy complication marked by high blood pressure and the presence of protein in the urine. Julie L. Lavoie studies this hormonal disruption involved in preeclampsia, a major pregnancy complication.

Hormonal regulation can also be disrupted by substances known as endocrine disruptors, which are found in certain plastics, pesticides, or cosmetic products. These substances can mimic or block the action of natural hormones. By interfering with estrogen receptors or hormonal signaling pathways, they may harm fertility, fetal development, and long-term health. Isabelle Plante’s research aims to understand how these disruptors affect mammary gland cells and how such deregulation may contribute to the development of breast cancer and other diseases. Cathy Vaillancourt’s team studies how exposure to environmental factors during pregnancy disrupts certain placental hormones, such as serotonin, melatonin, and glucocorticoids — which can influence fetal development in a sex-specific manner.