Men's Health Education: Analysis of the Impact of Trace Elements (Zinc, Manganese, Lead) on Fertility and Sexual Function

1. Trace Elements

Trace elements possess important physiological functions, nutritional roles, and clinical significance, and have attracted widespread attention in the medical community. They are closely related to many disciplines, including inorganic chemistry (or inorganic biochemistry), physiology, genetics, molecular biology, clinical medicine, botany and zoology, environmental science, medical geography, and pharmacology.

Elements can be divided into two main categories based on their content and requirements in the body: macroelements and trace elements. Macroelements comprise 99.5% of the total body weight and are the main components of the human body. These include oxygen (65.0%), carbon (18.0%), hydrogen (10.0%), nitrogen (0.3%), calcium (1.5%), phosphorus (1.0%), sulfur (0.25%), potassium (0.20%), sodium (0.15%), chlorine (0.15%), and magnesium (0.05%), totaling 11 elements, collectively referred to as macroelements. Elements comprising less than one ten-thousandth of the total body weight are called trace elements, including: F (fluorine), Si (silicon), V (vanadium), Cr (chromium), Mn (manganese), Fe (iron), Co (cobalt), Ni (nickel), Cu (copper), Zn (zinc), As (arsenic), Se (selenium), I (iodine), Pb (lead), Sr (strontium), Mo (molybdenum), etc. The WHO (1974) listed cobalt, iron, iodine, fluorine, zinc, copper, chromium, molybdenum, and selenium as essential nutrients for humans. Trace elements are closely related to human reproductive endocrine function and sexual function;

excess or deficiency of these elements can lead to infertility, reproductive endocrine disorders, or sexual dysfunction.

① Lead (Pb) Excessive lead can directly affect thyroid function in animals and patients, reducing iodine uptake and plasma protein-bound iodine (PBI) in the thyroid gland of rodents and humans. ① **Decrease in pituitary hormone secretion:** Excessive iron in the body has a significant adverse effect on the pancreas and gonads. It severely interferes with the gonads and reproductive system, causing underdeveloped or atrophied reproductive organs, oligomenorrhea or amenorrhea, and underdeveloped breasts. Excessive iron can lead to pancreatic atrophy, testicular spermatogenic cell atrophy, impaired anterior pituitary function, and reduced secretion of troponin-releasing hormones; it can also increase melanin content in the skin; some people may experience hypothyroidism and delayed puberty.

② **Excessive nickel (Ni):** Besides its carcinogenic and other harmful effects, excessive nickel also has adverse effects on the endocrine system. For example, excessive nickel can accelerate the release of prolactin-inhibiting factors, reducing the secretion of prolactin (PRL) through the hypothalamus and pituitary gland. Nickel can also interfere with the release of other hormones secreted by the pituitary gland and reproductive capacity, leading to reduced litter size in animals (Henkin, 1976).

④ Molybdenum (Mo): Excessive molybdenum intake in animals can cause severe testicular atrophy and decreased libido, resulting in reduced reproductive capacity; it also reduces the secretion of thyroid hormones and impairs growth and development. Aluminum and copper have antagonistic effects; excessive molybdenum can interfere with the absorption and utilization of copper, causing copper deficiency-like lesions. The normal daily molybdenum requirement for adults is 2 μg/kg.

⑤ Manganese (Mn): In manganese poisoning, excessive manganese in human tissues can inhibit the activity of tyrosine hydroxylase and dopamine decarboxylase, disrupting the biochemical processes of dopamine conversion, 5-hydroxytryptophan conversion to 5-HT, and phenylalanine conversion to dopamine. This leads to a decrease in the synthesis and content of dopamine and dopa in various tissues (especially the brain and adrenal cortex), resulting in disordered nerve conduction in the extrapyramidal system and causing various pathological changes such as Parkinson's syndrome. It can also secondaryly cause sexual dysfunction.

Manganese deficiency can cause growth retardation, skeletal deformities, and reproductive system abnormalities in animals. It can lead to ovarian dysfunction, testicular degeneration, seminiferous tubule degeneration, decreased libido and reduced sperm count, causing guinea pigs to lose their mating ability, irregular estrous cycles, and infertility.

⑥ Zinc (Zn) The total amount of zinc in a normal human body is about 33.3g, mainly concentrated in organs such as the testes, epididymis, and prostate, with particularly high concentrations in semen. Adults need 10-15mg of zinc daily; pregnant women need 25mg daily, and lactating women need 30-40mg daily. The concentration of zinc in blood plasma is approximately 75–115 μg/100ml, while the concentration in semen is 15–30 mg/100ml.

Animal experiments have shown that zinc deficiency can lead to stunted growth and development, weight loss, changes in skin and hair, testicular atrophy, reduced reproductive function or infertility. Even if spermatogenesis occurs and fertilization is possible, the miscarriage rate is high, and it easily causes congenital malformations in offspring. Zinc deficiency is also common in humans. The causes may include malnutrition, insufficient intake, or malabsorption. Common clinical symptoms of zinc deficiency include anorexia, weight loss, decreased olfactory sensitivity, abnormal taste, and delayed wound healing. In children, it can lead to significant developmental delays or dwarfism. Zinc is extremely important for growth, development, and sexual function; infants and children are particularly sensitive to zinc deficiency. Maternal zinc deficiency can cause fetal growth retardation, poor growth, and even malformations. Zinc deficiency can lead to male infertility, characterized by low sperm count and poor sperm quality. After zinc supplementation, both sperm count and quality significantly improve, and fertility can be restored.

Zinc deficiency can also affect the pituitary gland's release of gonadotropins. Recent studies have shown a link between zinc deficiency and impotence, sexual dysfunction, decreased libido, and infertility associated with renal failure. Impotence during continuous dialysis for renal failure, sexual dysfunction in the late stages of kidney disease, abnormal sperm production, decreased libido, testicular atrophy, reduced plasma testosterone levels, and infertility are all caused by zinc deficiency. Recent reports indicate that zinc deficiency can occur during dialysis for renal failure, kidney transplantation, and general kidney diseases. Zinc treatment can indeed improve sexual function and cure impotence. These facts further illustrate the close relationship between zinc and sexual function.

⑦ Copper (Cu) Copper is an essential trace element in the human body, participating in the synthesis and activation of many enzymes. It plays an important role in electron transfer, redox reactions, tissue respiration, metabolism, endocrine gland function, and the formation of hormones and neurotransmitters. The average adult human body contains about 150mg of copper, mostly in bound form, with a small portion existing in a free state. Copper significantly affects sperm survival rate and motility, and influences the ability of sperm to penetrate cervical mucus. Excessive copper ion concentration in the whole body and local tissues can interfere with reproductive function. Excessive copper ion concentration in the uterine cavity can interfere with the female fertilization process, leading to infertility.

⑧ Arsenic (As) Arsenic is one of the most toxic trace elements and is the main component of arsenic trioxide (arsenic poisoning). However, animals deficient in arsenic have a very low percentage of offspring after mating, with only 58% of offspring surviving (compared to over 90% survival in the normal control group). Excessive exposure to arsenic fumes can cause gastrointestinal disturbances, dizziness, loss of appetite, fatigue, nervousness, or even depression.

⑨ The total amount of chromium (Cr) in an adult body is approximately 6 mg, which gradually decreases with age. Chromium deficiency reduces insulin activity and impairs glucose tolerance, potentially leading to glycosuria, fasting glycosuria, and diabetes, and can easily result in secondary sexual dysfunction.

2. Anticancer Drugs

In recent years, significant progress has been made in chemotherapy for tumors. For example, the MOPP regimen (nitrogen mustard + vincristine + prednisone) for treating male lymphosarcoma has achieved complete remission in a number of patients, but 80% of these patients experience severely reduced or absent spermatogenesis, often accompanied by testicular atrophy and elevated serum FSH levels. Adult testes are more sensitive to chemotherapy than pre-pubertal testes, but chemotherapy has a more pronounced impact on testicular function in adolescent males. This indicates that the degree of damage to the gonads caused by chemotherapy is influenced by age at the time of treatment. In younger patients, gonadal function or sexual function can often be restored to pre-illness levels after chemotherapy is discontinued or reduced.

3. Anticholinergic drugs and others. Anticholinergic drugs such as atropine and trihexyphenidyl can inhibit acetylcholine, thus suppressing the parasympathetic nervous system. Since the parasympathetic nervous system is related to maintaining normal penile erection and ejaculation, it can prevent the penis from reflexively becoming congested, leading to impotence. After using these drugs, women often experience decreased vaginal lubrication and sexual arousal disorders, as these phenomena are related to changes in the vascular congestion of vaginal tissues.