Impactul hormonilor artificiali de creştere asupra sistemului endocrin și reproductiv uman – metaanaliză

Introduction

The use of artificial hormones like estrogen, progesterone, testosterone, trenbolone acetate and zeranol is common in livestock farming to speed up growth and improve meat production, especially in beef cattle and sheep⁽¹⁷⁾. Although agencies like the Food and Drug Administration (FDA) regulate these practices and consider them safe, concerns remain about hormone residues in meat possibly disrupting human hormonal balance and causing reproductive health problems⁽¹⁵⁾. The European Union’s ban on hormone use in meat shows ongoing debates about their safety and effects on health⁽⁵⁾. This study explores how artificial hormones in animal products may impact human reproductive and endocrine systems, highlighting the importance of strict regulation and more research.

Common types of livestock

Livestock is important worldwide for providing key foods like meat, milk, eggs and fiber, supporting both food security and rural livelihoods. Cattle are essential for beef and dairy, supplying high-quality protein, iron and vitamins B₁₂ and D, which help muscle growth, red blood cells and bones⁽⁴⁾. Pigs provide pork, rich in protein, zinc and B vitamins that boost energy and immunity. Chickens offer meat and eggs packed with protein, selenium, niacin and choline, which support metabolism, immune health and brain function. Goats produce easily digestible milk, lean meat and fiber, with their milk containing probiotics and minerals like calcium and potassium. Sheep supply wool and meat like lamb and mutton, rich in protein, zinc and vitamin B₁₂. To meet growing demand, many farmers use hormone treatments to increase production⁽²⁴⁾.

In Sri Lanka, livestock farming is important for providing nutrients, improving diets and in supporting income and jobs in rural areas⁽²⁵⁾. Products like milk, meat and eggs contribute to both the local economy and exports^(6,18). Livestock also helps small farmers by turning crop leftovers into valuable animal products. In regions such as the Northern and Eastern provinces, cattle and goat farming are common, while dairy farming is especially strong in the Central Province, including Nuwara-Eliya⁽²⁾.

Artificial hormones

Artificial hormones are synthetic chemicals commonly used in modern livestock farming to boost productivity and efficiency. These hormones are administered to various animal species such as pigs, chickens, sheep and cattle⁽²⁸⁾. Countries with large-scale agricultural industries, such as the United States of America, Brazil and China, use these hormones extensively to maximize productivity. The use of synthetic hormones helps improve growth rates, milk production and feed efficiency, enabling farmers to meet the increasing global demand for animal products⁽²⁸⁾. However, there are concerns about the potential risks associated with their use, including long-term effects on human health and animal welfare⁽⁶⁾.

Common types of artificial hormones used in livestock and their purpose

Various artificial hormones are used in livestock farming to improve growth, reproduction and productivity. Growth hormones like recombinant bovine somatotropin (rBST) and trenbolone acetate help cattle, pigs and poultry grow faster and more efficiently, reducing the time needed to reach market weight⁽¹¹⁾. In cattle and buffaloes, hormones such as diethylstilbestrol (DES), testosterone and trenbolone boost weight gain and milk production⁽¹³⁾. Pigs are also given trenbolone to build lean muscle and reduce fat. Reproductive hormones like progesterone and estradiol-17b are used to regulate fertility and synchronize breeding in animals like cattle, sheep and goats. For dairy animals, oxytocin helps release milk, while melengestrol acetate (MGA) supports regular breeding cycles and milk production. In poultry, estradiol-17b is used to improve egg production and consistency⁽¹⁹⁾.

Possible risk factors worldwide

The use of artificial hormones in livestock farming raises major concerns for human health, the environment and animal welfare. Hormone-treated meat has been linked to fertility problems, reproductive issues and a higher risk of certain cancers⁽¹⁰⁾. Using hormones with antibiotics can also lead to antibiotic-resistant bacteria that may spread to humans through food. Hormone residues can pollute water and soil, harming wildlife and ecosystems. There are also ethical concerns about the unnatural growth of animals caused by hormones⁽²⁴⁾. As a result, the European Union has banned growth hormones, while countries like the U.S. still allow them under regulation⁽⁵⁾. The WHO and FAO recommend stronger rules to reduce these risks⁽⁶⁾. Sustainable farming methods, like organic and regenerative agriculture, offer safer alternatives that protect human and animal health and the environment. This study focuses on how hormone-treated animal products may affect human reproductive and endocrine health as global meat and dairy consumption continues to rise.

Methodology

This study employed a meta-analysis approach to systematically review the existing research on the effects of artificial hormones in livestock on human health. A comprehensive literature search was conducted using Google Scholar, PubMed and ResearchGate to gather relevant peer-reviewed articles.

To gather accurate and relevant data, a clear and organized search was done using specific keywords like “livestock artificial hormones”, “human health effects of artificial hormones” and “hormone residues in animal products”. These terms covered both scientific and health concerns about hormone use in livestock. The search took place in trusted databases like PubMed, Google Scholar and ResearchGate to find reliable sources. Only articles published after 2012 that had strong research methods, good sample sizes and focused on human health effects from hormone-treated animal products were included. This careful process made sure the study used up-to-date and trustworthy information for a thorough analysis.

The inclusion and exclusion criteria

The inclusion and exclusion criteria were set to ensure the selected studies were relevant, reliable and high-quality. Studies were included if they focused on human participants and the health effects of consuming hormone-treated animal products, were published after 2012, and appeared in peer-reviewed journals. Studies were excluded if they were based only on animals, combined hormones with other drugs, were not in English, or lacked clear methods or sufficient data. This approach helped maintain a clear focus and ensured the findings were credible and up to date.

The study selection was conducted in four stages, using the PRISMA framework. In the Identification stage, an initial search yielded 72 articles from selected databases. During the Screening stage, titles and abstracts were reviewed, resulting in the exclusion of 33 studies due to irrelevance or duplication. In the Eligibility stage, full-text reviews were conducted on 39 studies, with the inclusion and exclusion criteria applied. Finally, in the Final Selection stage, 25 high-quality studies were selected for quantitative synthesis in the meta-analysis. A PRISMA flow diagram was used to illustrate the study selection process (Figure 1).

Results and discussion

Consumable live stocks

Artificial hormones are commonly used in livestock farming in countries like the United States of America, Canada, the European Union, and parts of Asia and South America to help animals like chickens, pigs and cattle grow faster and use feed better⁽²⁹⁾. However, their use has raised health concerns, such as hormone imbalances and reproductive problems in humans^(3,22). Because of these worries, the European Union has banned growth hormones in livestock, while the U.S. and Canada still allow them but with different rules⁽⁶⁾. This difference shows ongoing debates about food safety, as more consumers ask for hormone-free or organic meat and dairy. These concerns also highlight growing public interest in health and environmental issues, pushing for better labeling and stricter farming rules.

Artificial hormones in livestock 

Artificial hormones are widely used in livestock farming in countries like the United States, Canada, the European Union, and parts of Asia and South America to help animals such as chickens, pigs, and cattle grow faster and use feed more efficiently⁽²⁷⁾. However, their use has raised health concerns, including hormone imbalances and reproductive problems in humans⁽⁷⁾. Because of these concerns, the European Union has banned growth hormones in livestock, while the U.S. and Canada still allow them under different regulations⁽⁷⁾. This difference highlights ongoing debates about food safety and reflects growing consumer demand for hormone-free or organic meat and dairy products, as well as increased interest in health and environmental issues, leading to calls for better labeling and stricter farming rules.

Major types of food items supposed to have high amounts of artificial hormones 

Dairy and beef production rely heavily on artificial hormones to increase growth and milk yield. In beef cattle, hormones like natural testosterone, estradiol and synthetic compounds such as zeranol help speed up muscle growth and improve feed efficiency, allowing animals to reach market weight faster⁽²¹⁾. In dairy farming, recombinant bovine somatotropin (rBST) is commonly used to boost milk production by stimulating the cow’s mammary glands⁽¹²⁾. Other hormones like progesterone and estrogen help regulate reproduction in dairy cows⁽²³⁾. While these hormones improve productivity and meet growing food demand, concerns remain about hormone residues in meat and dairy products and their possible effects on human health. This has led to calls for stricter regulation and ongoing monitoring to ensure food safety and protect consumers.

Synthetic hormones like zeranol work by mimicking natural estrogen, promoting muscle growth and reducing fat in cattle through biochemical processes⁽²⁰⁾. They offer advantages over natural hormones by being more stable and easier to control, resulting in consistent animal growth⁽⁸⁾. However, debates continue about the long-term health impacts of consuming hormone-treated products, prompting demands for more research and tighter regulations. Despite these concerns, artificial hormones remain important tools in livestock farming to meet global demand. Balancing productivity, animal welfare and consumer safety requires transparency, regulation and further studies to ensure a sustainable and trustworthy food supply⁽⁶⁾.

Effect of consumable livestock containing artificial hormones on human reproductive system

Artificial hormones are widely used in livestock farming to boost growth, reproduction and milk production, but growing research shows they may harm human reproductive health. Studies have found that synthetic hormones like testosterone, estradiol and trenbolone can reduce sperm count and motility in men, disrupt hormone balance, and lead to conditions such as erectile dysfunction and benign prostatic hyperplasia⁽²⁶⁾. In women, hormones like norethisterone, medroxyprogesterone acetate, diethylstilbestrol and zeranol have been linked to irregular menstruation, ovulatory problems and fertility issues, including polycystic ovary syndrome⁽³²⁾. Synthetic hormone residues can also lower egg quality and harm reproductive development in offspring exposed prenatally. These findings highlight the urgent need for further research and tighter control over hormone use in livestock.

Beyond fertility problems, synthetic hormones may increase the risk of hormone-related cancers. Exposure to artificial estrogens is associated with higher risks of breast, ovarian and prostate cancers⁽¹⁶⁾. Synthetic growth hormones may promote abnormal cell growth linked to cancer. Epigenetic studies also suggest that early exposure to synthetic hormones can cause long-term gene changes that raise cancer risk later in life⁽³¹⁾. Given the strong evidence connecting hormone residues in animal products to reproductive disorders and cancers, stricter regulation, better monitoring and public awareness are critical to protect human health. Encouraging reduced consumption of hormone-treated meat and dairy, alongside ongoing research, can help minimize these risks.

Effect of consumable livestock containing artificial hormones on human endocrine system

Synthetic hormones used in livestock farming, such as estradiol, progesterone, trenbolone and zeranol, can disrupt the human endocrine system when residues remain in meat, milk and eggs. These hormones affect key glands like the hypothalamus, thyroid, adrenal glands, pancreas and pituitary, leading to problems such as thyroid dysfunction, insulin resistance, metabolic disorders and reproductive issues⁽¹⁾. For example, synthetic hormones can disturb the appetite-regulating hormones, causing overeating or irregular eating habits and contributing to obesity⁽³⁰⁾. They can also interfere with thyroid hormone balance, leading to fatigue and weight changes, and disrupt adrenal cortisol production, which affects stress response and immune function. These impacts show the need for careful monitoring of hormone residues in food to protect human health. Further, synthetic hormones can impair the reproductive health by disrupting the pituitary gland’s secretion of hormones essential for fertility and growth⁽¹⁴⁾. They also affect sleep cycles by interfering with melatonin production, causing fatigue and memory issues⁽⁹⁾. The long-term consumption of hormone-treated animal products may increase the risks for metabolic and reproductive disorders, highlighting the importance of stricter regulations on hormone use in livestock farming. Ongoing research is necessary to better understand and manage the health risks posed by synthetic hormones in food.

Conclusions

This study highlights the serious health risks associated with artificial hormones used in cattle farming, particularly their negative effects on the human reproductive and endocrine systems. Even in small amounts, hormones like trenbolone, progesterone, testosterone, estradiol and zeranol can cause hormone imbalances, fertility problems and metabolic disorders. These hormones may also affect other body systems, leading to issues such as weakened immunity, heart problems, bone disorders, digestive issues and neurological effects. The presence of hormone residues in meat and dairy products underscores the need for stronger regulations, improved testing and better consumer education. Raising awareness and conducting more research on the long-term effects of low-level hormone exposure are essential steps toward reducing health risks and ensuring a safer food supply.   

Corresponding author: Faiz Marikar E-mail: faiz@kdu.ac.lk

Conflict of interest: none declared.

Financial support: none declared.

This work is permanently accessible online free of charge and published under the CC-BY licence.