What Is: Hormones

The "Chemical Messenger"
The Endocrine System and Chemical Communication
Image Credit: Scientific Frontline

The Silent Orchestrators

Hormones are the silent orchestrators of the human body. They are the unseen chemical messengers that, in infinitesimally small quantities, conduct the complex symphony of life. These powerful molecules control and regulate nearly every critical function, from our mood, sleep, and metabolism to our growth, energy levels, and reproductive functions.

At its most fundamental level, a hormone is a chemical substance produced by a gland, organ, or specialized tissue in one part of the body. It is then released—typically into the bloodstream—to travel to other parts of the body, where it acts on specific "target cells" to coordinate function.

The power of this system, which has identified over 50 distinct hormones in humans, lies in its exquisite specificity. Although hormones circulate throughout the entire body, reaching every cell, they only affect the cells that are equipped to listen. This is governed by the "lock and key" principle: target cells possess specific "receptors," either on their surface or inside the cell, that are shaped to bind only to a compatible hormone. This report will delve into the world of these powerful molecules, exploring the intricate system that creates them, the chemical language they speak, and the profound, lifelong impact they have on our daily health and well-being.

Better mental health found among transgender people who started hormones as teens

For transgender people, starting gender-affirming hormone treatment in adolescence is linked to better mental health than waiting until adulthood, according to new research led by the Stanford University School of Medicine.

The study, which appeared online Jan. 12 in PLOS ONE, drew on data from the largest-ever survey of U.S. transgender adults, a group of more than 27,000 people who responded in 2015. The new study found that transgender people who began hormone treatment in adolescence had fewer thoughts of suicide, were less likely to experience major mental health disorders and had fewer problems with substance abuse than those who started hormones in adulthood. The study also documented better mental health among those who received hormones at any age than those who desired but never received the treatment.

Gender-affirming hormone treatment with estrogen or testosterone can help bring a transgender person’s physical characteristics in line with their gender identity. In adolescence, hormone therapy can enable a transgender teenager to go through puberty in a way that matches their gender identity.

“This study is particularly relevant now because many state legislatures are introducing bills that would outlaw this kind of care for transgender youth,” said Jack Turban, MD, a postdoctoral scholar in pediatric and adolescent psychiatry at Stanford Medicine. “We are adding to the evidence base that shows why gender-affirming care is beneficial from a mental health perspective.”

Turban is the study’s lead author. The senior author is Alex Keuroghlian, MD, associate professor of psychiatry at Harvard Medical School and director of the National LGBTQIA+ Health Education Center at the Fenway Institute.

Cannabis and Male Testosterone Levels

Although cannabis appears to disrupt certain biological mechanisms related to reproduction, the exact clinical consequences on the fertility of young men are still being studied.
Photo Credit: Esteban López

Scientific Frontline: Extended "At a Glance" Summary: Cannabis Use and Male Testosterone Levels

The Core Concept: A recent study demonstrates that cannabis use in young men does not reduce testosterone levels, but instead appears to increase the testicular synthesis of the hormone by approximately 23%.

Key Distinction/Mechanism: Contrary to earlier assumptions that cannabis decreases male sex hormones, this research localized the testosterone increase specifically to the testes (Leydig cells), rather than the adrenal glands. Importantly, the study clarifies that this hormonal spike does not equate to improved sperm quality or overall fertility and may represent a compensatory physiological response.

Major Frameworks/Components:

• Extensive steroid profiling that analyzed hundreds of hormones (including androgens, progestogens, and estrogens), expanding significantly beyond isolated testosterone screening.
• Examination of the endocannabinoid system's interaction with male reproductive biology.
• The isolation of two novel metabolic biomarkers indicating regular cannabis exposure: hydroxyprogesterone (11B-OHP4) and dihydroprogesterone (5B-DHP4).

Components of Cytoskeleton Strengthen Effect of Sex Hormones

Super-high-resolution microscopic image of a cell that has been exposed to the sex hormone dihydrotestosterone. The androgen receptor (violet) and actin (green) are visible in the cell nucleus. Both molecules are stained with fluorescent dyes and thus made visible. The individual structures made visible (right) are only 200 nanometers (200 millionths of a millimeter) small.
Image Credit: Julian Knerr/University of Freiburg

Researchers from Freiburg and Kiel discover that actin acts in the cell nucleus and is partly responsible for the expression of male sexual characteristics

Steroid hormones, to which belong sex hormones like estrogen or testosterone, are important signaling molecules and are responsible among other things for controlling female and male phenotypic sex differentiation. They act by binding to receptor molecules that switch on and off the activity of hormone-dependent genes. Researchers at the University of Freiburg and Kiel University Hospital have discovered that components of the cytoskeleton are critically involved in this process. The findings are relevant for the diagnosis of medical conditions and the study of diseases and cancers in which steroid hormones play important roles. The study was published in the renowned journal Nature.

The new research findings show that filamentous actin, a component of the cytoskeleton, interacts with the androgen receptor directly in the cell nucleus and strengthens its effect. The androgen receptor mediates the signals of sex hormones for male sex development but also promotes the progression of prostate cancer.

Neuroendocrinology: In-Depth Description

Neuroendocrinology is the scientific study of the complex, bidirectional interactions between the nervous system and the endocrine system. Its primary goal is to elucidate how the brain—particularly the hypothalamus—regulates the synthesis and secretion of hormones, and conversely, how circulating hormones modulate neural function, neuroplasticity, and behavior.

Endocrinology: In-Depth Description

Endocrinology is the branch of biology and medicine focused on the study of the endocrine system, its diseases, and its specific secretions known as hormones. The primary goal of this field is to understand how these chemical messengers coordinate and regulate complex bodily functions—ranging from metabolism and cellular growth to reproduction and circadian rhythms—and to diagnose, manage, and treat disorders that arise when hormone production or receptor signaling is disrupted.

A delicate balance between growth hormone and stem cells

Andrei Chagin, Institute of Medicine, Sahlgrenska Academy at the University of Gothenburg.
Photo Credit: Magnus Gotander

Researchers at the University of Gothenburg can now demonstrate previously unexplained processes behind growth therapy. It involves hormonal mechanisms at the cellular level, with focus on a sensitive balance between stem cells and growth hormone. 

When children grow in length, it occurs from growth plates, a cartilage structure at both ends of the long bones found in the arms and legs. The growth plates contain special stem cells that continuously produce new cartilage cells, which are converted into bone tissue. 

In the case of growth disorders in children, with a height significantly below the average for their age and sex, injections of growth hormone are the most common treatment. In the development of growth hormone therapy, the University of Gothenburg has played a historically important role  

Previous research has shown that growth hormones act directly on the growth plate. However, it has been unclear which cells are targeted by growth hormones and how. 

Mice study suggests metabolic diseases may be driven by gut microbiome, loss of ovarian hormones

Mice that received fecal implants from donors that had their ovaries removed gained more fat mass and had greater expression of liver genes associated with inflammation, Type 2 diabetes, fatty liver disease and atherosclerosis. The findings may shed light on the greater incidence of metabolic dysfunction in postmenopausal women. The team members included, from left: molecular and integrative physiology professor Erik R. Nelson; Kelly Swanson, the director of the Division of Nutritional Sciences and the Kraft Heinz Endowed Professor in Human Nutrition; and animal sciences professor Brett R. Loman.
  Photo Credit: Fred Zwicky

The gut microbiome interacts with the loss of female sex hormones to exacerbate metabolic disease, including weight gain, fat in the liver and the expression of genes linked with inflammation, researchers found in a new rodent study.

The findings, published in the journal Gut Microbes, may shed light on why women are at significantly greater risk of metabolic diseases such as obesity and Type 2 diabetes after menopause, when ovarian production of female sex hormones diminishes.

“Collectively, the findings demonstrate that removal of the ovaries and female hormones led to increased permeability and inflammation of the gut and metabolic organs, and the high-fat diet exacerbated these conditions,” said Kelly S. Swanson, the director of the Division of Nutritional Sciences and the Kraft Heinz Endowed Professor in Human Nutrition at the University of Illinois Urbana-Champaign who is a corresponding author of the paper.  “The results indicated that the gut microbiome responds to changes in female hormones and worsens metabolic dysfunction.”

Researchers create artificial enzyme for fast detection of disease-related hormone in sweat

Photo Credit: Courtesy of Oregon State University

Researchers in the Oregon State University College of Engineering have developed a handheld sensor that tests perspiration for cortisol and provides results in eight minutes, a key advance in monitoring a hormone whose levels are a marker for many illnesses including various cancers.

Findings were published in the journal ACS Applied Materials & Interfaces. The material and sensing mechanism in the new device could be easily engineered to detect other specific hormones, the researchers say – for example, progesterone, a key marker for women’s reproductive health and pregnancy outcomes.

“We took inspiration from the natural enzymes used in blood glucose meters sold at pharmacies,” said Larry Cheng, associate professor of electrical engineering and computer science. "In glucose meters, specific enzymes are applied to an electrode, where they can capture and react with glucose molecules to generate an electrical signal for detection. However, finding natural enzymes for cortisol detection is not straightforward, and natural enzymes are prone to instability and have a short lifespan.

Nanotube sensors are capable of detecting and distinguishing gibberellin plant hormones

The continued study of gibberellins could lead to further breakthroughs in agricultural science and have implications for food security.
Photo Credit: Courtesy of SMART.

Researchers from the Disruptive and Sustainable Technologies for Agricultural Precision (DiSTAP) interdisciplinary research group of the Singapore-MIT Alliance for Research and Technology (SMART), MIT’s research enterprise in Singapore, and their collaborators from Temasek Life Sciences Laboratory have developed the first-ever nanosensor that can detect and distinguish gibberellins (GAs), a class of hormones in plants that are important for growth. The novel nanosensors are nondestructive, unlike conventional collection methods, and have been successfully tested in living plants. Applied in the field for early-stage plant stress monitoring, the sensors could prove transformative for agriculture and plant biotechnology, giving farmers interested in high-tech precision agriculture and crop management a valuable tool to optimize yield.

The researchers designed near-infrared fluorescent carbon nanotube sensors that are capable of detecting and distinguishing two plant hormones, GA3 and GA4. Belonging to a class of plant hormones known as gibberellins, GA3 and GA4 are diterpenoid phytohormones produced by plants that play an important role in modulating diverse processes involved in plant growth and development. GAs are thought to have played a role in the driving forces behind the “green revolution” of the 1960s, which was in turn credited with averting famine and saving the lives of many worldwide. The continued study of gibberellins could lead to further breakthroughs in agricultural science and have implications for food security.

Study finds stress-related nerves may fuel pancreatic cancer growth

Ariana Sattler, Ph.D., right, and Ece Eksi, Ph.D., are co-authors on a new study that found that certain nerves may support pancreatic cancer growth.
Photo Credit: OHSU/Christine Torres Hicks

Scientific Frontline: Extended "At a Glance" Summary: The Role of Sympathetic Nerves in Pancreatic Cancer

The Core Concept: Sympathetic nerves, which regulate the body's "fight or flight" stress response, can infiltrate pancreatic tumors and actively facilitate their growth by communicating with cancer cells and surrounding support cells.

Key Distinction/Mechanism: Traditional oncology has heavily focused on intra-tumor components like immune cells, blood vessels, and fibroblasts while largely overlooking the nervous system, as the main bodies of nerve cells reside outside the tumor. This new paradigm demonstrates that nerves structurally infiltrate the tumor microenvironment and chemically alter the behavior of cancer cells and cancer-associated fibroblasts to promote malignancy.

Major Frameworks/Components: 

• Tumor Microenvironment Integration: Sympathetic nerves act as an external support system, directly embedding into and altering the pancreatic tumor ecosystem.
• Prognostic Genetic Markers: The presence of sympathetic-associated genes correlates with poor survival rates in human patients with pancreatic cancer.
• Sex-Specific Phenotypes: Experimental removal of sympathetic nerves in mouse models resulted in reduced tumor size exclusively in female mice, suggesting that sex hormones heavily influence nerve-tumor communication.

How Did Humans Develop Sharp Vision? Lab-Grown Retinas Show Likely Answer

Image representation
Image Credit: Scientific Frontline

Scientific Frontline: Extended "At a Glance" Summary: Retina Organoids & Human Vision

The Core Concept: Retina organoids are lab-grown, three-dimensional clusters of retinal tissue derived from fetal cells that replicate the developmental processes of the human eye in a controlled environment.

Key Distinction/Mechanism: Unlike previous models which suggested blue cone cells physically migrated out of the central retina (foveola), these organoids revealed that cells undergo a conversion process. The mechanism is two-fold: retinoic acid (a vitamin A derivative) breaks down to limit the initial creation of blue cones, and thyroid hormones subsequently signal the remaining blue cones to transform into red and green cones, establishing the specialized pattern required for sharp daytime vision.

Origin/History: The findings were published in the Proceedings of the National Academy of Sciences around February 18, 2026. This research challenges a prevailing 30-year-old biological theory regarding how the eye distributes light-sensing cells during development.

Major Frameworks/Components:

• Organoid Technology: The cultivation of "mini-retinas" in petri dishes to observe long-term developmental timelines.
• The Foveola: The specific central region of the retina responsible for 50% of visual perception and high-acuity vision.
• Cell Fate Specification: The biological programming that determines whether a photoreceptor becomes a blue, green, or red cone.
• Hormonal Signaling: The specific interplay between retinoic acid and thyroid hormones in dictating cell identity.

Common drug offers fertility hope for women with obesity

Researchers may have found a solution to improving fertility in women with obesity, following a successful trial in mice using diabetes medication to reduce blood glucose levels.

The University of Queensland study found the common type 2 diabetes medication, Dapagliflozin, altered reproductive hormones in obese mice, and could be the key to improving fertility in humans.

Professor Chen Chen, from UQ’s School of Biomedical Sciences, said the results were a promising sign, as human and mouse reproductive cycles are similar.

“After eight weeks of treatment, blood glucose levels in the mice normalized, body weight reduced, reproductive cycles recovered, and reproductive hormones and ovulation were largely restored, compared with mice that were not treated,” Professor Chen said.

“The drug we used – Dapagliflozin – is known for reducing blood glucose levels and improving other biomarkers of metabolic health, but its effects on reproductive health and fertility have yet to be fully investigated.

“Our findings suggest that normalizing blood glucose metabolism with Dapagliflozin in obesity may be a promising route for restoring reproductive function, at the very least.”

First atlas of the human ovary with cell-level resolution is a step toward artificial ovary

University of Michigan BME graduate student Jordan Machlin shows to prof. Ariella Shikanov and fellows grad student Margaret Brunette the images of oocytes in ovarian tissue she collected using RNA-fluorescence in situ hybridization.
Photo Credit: Marcin Szczepanski/Lead Multimedia Storyteller, Michigan Engineering

A new “atlas” of the human ovary provides insights that could lead to treatments restoring ovarian hormone production and the ability to have biologically related children, according to University of Michigan engineers.

This deeper understanding of the ovary means researchers could potentially create artificial ovaries in the lab using tissues that were stored and frozen before exposure to toxic medical treatments such as chemotherapy and radiation. Currently, surgeons can implant previously frozen ovarian tissue to temporarily restore hormone and egg production. However, this does not work for long because so few follicles—the structures that produce hormones and carry eggs—survive through reimplantation, the researchers say.

The new atlas reveals the factors that enable a follicle to mature, as most follicles wither away without releasing hormones or an egg. Using new tools that can identify what genes are being expressed at a single-cell level within a tissue, the team was able to home in on ovarian follicles that carry the immature precursors of eggs, known as oocytes.

Stress increases Alzheimer’s risk in female mice but not males

Stress causes the levels of Alzheimer's proteins to rise in females' brains but not males' brains, according to a new study in mice by researchers at Washington University School of Medicine in St. Louis. This difference may contribute to women's greater risk of developing Alzheimer's disease.
Photo Credit: Karolina Grabowska

Women are about twice as likely as men to be diagnosed with Alzheimer’s disease. Some of that is age; in the U.S., women outlive men by five to six years, and advanced age is the strongest risk factor for Alzheimer’s. But there’s more to it than that, so Alzheimer’s researchers continue to look for other reasons why women have an elevated risk of the deadly neurodegenerative disease.

Stress may be one such reason. A study by researchers at Washington University School of Medicine in St. Louis shows that the effect stress has on the brain differs by sex, at least in mice. In stressful situations, levels of the Alzheimer’s protein amyloid beta rises sharply in the brains of females but not males. In addition, the researchers identified a molecular pathway that is active in brain cells from female mice but not male mice, and showed that it accounts for the divergent responses to stress.

The findings, published May 2 in Brain, add to a growing collection of evidence that sex matters in health and disease. From cancer to heart disease to arthritis, scientists have found differences between males and females that could potentially affect how men and women respond to efforts to prevent or treat chronic diseases.

Researchers reveal scale of prevalence of a condition that can cause type 2 diabetes and high blood pressure

Scientists at the University of Birmingham are calling for changes to healthcare policy following research which has shown for the first time the scale of the impact of a condition associated with benign tumors that can lead to type 2 diabetes and high blood pressure.

Up to 10 per cent of adults have a benign tumor, or lump, known as an ‘adrenal incidentaloma’ in their adrenals – glands situated on top of the kidneys which produce a variety of hormones. The lumps can be associated with the overproduction of hormones including the stress steroid hormone cortisol, which can lead to type 2 diabetes and high blood pressure. Previous small studies suggested that one in three adrenal incidentalomas produce excess cortisol, a condition called Mild Autonomous Cortisol Secretion (MACS).

Now, an international research team led by the University of Birmingham in the UK has carried out the largest ever prospective study of over 1,305 patients with adrenal incidentalomas to assess their risk of high blood pressure and type 2 diabetes and their cortisol production, comparing patients with and without MACS. The study is also the first to undertake a detailed analysis of the steroid hormone production in patients by analyzing cortisol and related hormones by mass spectrometry in 24-hour urine samples they collected.

Their study findings, published today in journal Annals of Internal Medicine, show that MACS is much more prevalent than previously reported: with almost every second patient in the study with an adrenal incidentaloma having MACS. Notably, 70% of patients with MACS were women and most of them were of postmenopausal age (aged over 50). Following their findings, the researchers now estimate that up to 1.3 million adults in the UK could have MACS. Considering that around two out of three of these patients are women, MACS is potentially a key contributor to women’s metabolic health, in particular in women after the menopause.

Clinically relevant deficiency of the “bonding hormone” oxytocin demonstrated

The hormones oxytocin and vasopressin are produced in the same area of the brain and are also very similar in structure. This is why disorders that cause vasopressin deficiency could also affect the neurons that produce oxytocin
Image Credit: Colin Behrens

The hormone oxytocin is important for social interaction and to control emotions. A deficiency of this hormone has previously been assumed, for example, in people with autism, but has never been proven. Now, for the first time, researchers from the University of Basel and the University Hospital of Basel have succeeded in demonstrating a deficiency of oxytocin in patients with a deficiency of vasopressin caused by a disease of the pituitary gland. This finding could be key to developing new therapeutic approaches.

The hormones oxytocin and vasopressin are produced in the same area of the brain and are also very similar in structure. Patients with a rare deficiency of vasopressin cannot concentrate their urine and lose liters of water as a result. In order to compensate for this loss, they are obliged to drink up to 10 liters or more per day.

With a nasal spray or a tablet containing synthetically produced vasopressin, these symptoms can usually be treated without any problems. However, even with this treatment, many patients report anxiety, have trouble with social interactions or demonstrate impaired emotional awareness.

Brain cell discovery sparks hope for fertility treatments

Photo Credit: Yoshihisa Uenoyama, Graduate School of Bioagricultural Sciences, Nagoya University

Researchers at Nagoya University’s Graduate School of Bioagricultural Sciences and the National Institute of Physiological Sciences in Japan have demonstrated how a specific type of neuron in the brain affects the release of hormones that control ovarian function, such as follicular development and ovulation in females. These findings, published in the journal Scientific Reports, could help researchers understand and treat reproductive disorders in both animals and humans.  

Kisspeptin neurons in the brain regulate the release of hypothalamic gonadotropin-releasing hormone (GnRH) and pituitary follicle-stimulating hormone/luteinizing hormone (LH). This process is important for reproduction, as pituitary hormones stimulate the ovaries to perform their reproductive functions. Examples include follicular development and ovulation in all mammals, including humans.   

There are two main areas of the brain involved in the process: the arcuate nucleus (ARC), in which kisspeptin neurons maintain the regular rhythmic (pulsatile) secretion of GnRH/LH that maintains normal follicular development and sex steroid production; and the anteroventral periventricular nucleus (AVPV), in which kisspeptin neurons trigger a surge of GnRH/LH that leads to ovulation.  

New Research Suggests Why Males and Females Respond Differently to Social Stress

Emily Wright, researcher, in a UC Davis lab.
Photo Credit: Jerry Tsai

Women are nearly twice as likely as men to be diagnosed with an anxiety disorder, but among boys and girls the likelihood is the same. New University of California, Davis, research has identified changes in the brain during puberty that may account for differences in how women and men respond to stress.

A team of psychologists has found that testosterone is the key hormone that drives gender-based differences in responses to social stress. The study encompassed six separate experiments with mice to isolate what changes in the brain drive these differences between males and females. The study was published in the Proceedings of the National Academy of Sciences, or PNAS, today.

“This research shows how the body’s hormones shape the complex interplay between the brain’s circuitry and behavioral responses to stress,” said Brian Trainor, a professor of psychology in the College of Letters and Science at UC Davis and the study’s corresponding author.

Even small amounts of licorice raise blood pressure

Researchers have studied how licorice affects blood pressure, among other things.
Photo Credit: Marion Wellmann

It is known that large amounts of licorice cause high blood pressure. A study by researchers at Linköping University now shows that even small amounts of licorice raise blood pressure. The individuals who react most strongly also show signs of strain on the heart.

Licorice is produced from the root of plants of the Glycyrrhiza species and has long been used as an herbal remedy and flavoring. However, it is known that eating licorice can also raise blood pressure. This is mainly due to a substance called glycyrrhizic acid that affects the body’s fluid balance through effects on an enzyme in the kidney. High blood pressure, in turn, increases the risk of cardiovascular disease.

Both the European Union and the World Health Organization have concluded that 100 mg of glycyrrhizic acid per day is probably safe to eat for most individuals. But some people eat more licorice than that. The Swedish Food Agency has estimated that 5 per cent of Swedes have an intake higher than this level.