Blood Sugar and Male Hormones: Testosterone, Metabolic Health and Fertility
Testosterone is often discussed in relation to muscle, libido and ageing. It also sits within a wider picture of metabolic health, sleep, nutrition and reproductive function.
Insulin resistance and type 2 diabetes are associated with lower testosterone in men. However, this does not mean that every man with tiredness needs a testosterone booster, or that raising testosterone is the best way to treat blood sugar.
What’s covered
- The relationship between insulin resistance, SHBG and testosterone.
- Symptoms, testing and the importance of sleep.
- Sexual health and fertility.
- Food, strength training and adequate energy intake.
- Zinc, magnesium, vitamin D, creatine and testosterone supplements.
- When medical care is needed.
Insulin resistance and testosterone
Insulin helps regulate glucose use and storage. When tissues become less responsive, the pancreas may produce more to maintain blood glucose. This can precede prediabetes or type 2 diabetes. [1]
Men with obesity, insulin resistance or type 2 diabetes often have lower total testosterone. One contributor is lower SHBG, the protein that carries testosterone in the blood. Lower total testosterone may partly reflect this transport change, rather than a corresponding fall in free testosterone. [2]
In some men, obesity and other health problems also suppress the signals from the hypothalamus and pituitary to the testes. Medicines, illness and testicular or pituitary conditions can contribute too. These possibilities matter because treatment depends on the cause. [2]
Symptoms and testing
Reduced libido, fewer spontaneous erections and sexual difficulties may prompt assessment. Fatigue, reduced strength and low mood can occur too, but are less specific and have many possible explanations.
The Endocrine Society recommends diagnosing testosterone deficiency only when compatible symptoms occur alongside unequivocally and consistently low testosterone. This usually involves repeating a morning fasting test. Where SHBG is altered, an appropriately measured or calculated free testosterone may help interpretation. Further hormone tests can help distinguish testicular from pituitary or hypothalamic causes. [2]
A single low result during illness, after poor sleep or in another temporary circumstance may not establish a lasting deficiency.
Sleep, stress and recovery
Sleep problems can affect energy, sexual health and metabolic regulation. Obstructive sleep apnoea is particularly relevant when there is loud snoring, witnessed pauses in breathing, morning headaches or daytime sleepiness.
It deserves assessment in its own right. Untreated severe sleep apnoea is also a reason for caution before testosterone therapy. Stress management can support wellbeing, but persistent symptoms should not automatically be labelled a cortisol problem. [2]
Sexual function and fertility
Erectile difficulties are not always caused by low testosterone. Blood vessel health, diabetes-related nerve damage, medicines, psychological factors and relationship circumstances can all contribute. Persistent erectile dysfunction deserves medical assessment, including cardiovascular risk where appropriate. [3]
Fertility also needs its own evaluation. A testosterone blood result does not tell us whether sperm count or quality is normal.
Testosterone therapy can suppress sperm production. Men who want children, now or in the near future, should discuss this before starting treatment. The same concern applies to anabolic steroids and unregulated hormonal products. Specialist assessment may identify more appropriate options. [2,4]
Nutrition that supports metabolic and reproductive health
Build a consistent eating pattern
Base meals around vegetables, fruit, pulses, wholegrains, suitable protein foods and unsaturated fats. Include protein across meals and enough fibre, rather than relying on protein powders while the rest of the diet remains limited.
A breakfast of oats, yoghurt or fortified soya yoghurt, seeds and berries is one option. Lunch might be a bean and tuna salad with wholegrain bread, or a tofu and vegetable bowl with brown rice.
There is no proven food combination that reliably raises testosterone in otherwise well-nourished men. The useful goal is adequate nutrition and better overall health.
Avoid crash diets and under-fuelling
Very low energy intake and excessive exercise can suppress reproductive hormone signalling. A plan that supports gradual, sustainable weight management when appropriate is different from repeatedly dieting hard and trying to compensate with supplements.
For men living with obesity, improvements in weight and metabolic health may improve testosterone levels, although the response varies and organic causes of deficiency still need investigation. [2]
Maintain muscle and move regularly
Resistance exercise supports strength and muscle, while walking and other aerobic activity support cardiovascular and metabolic health. Build activity gradually and allow recovery.
Exercise remains worthwhile even if it does not produce a large change in a testosterone blood result. Its benefits are broader than a single hormone.
Review alcohol and smoking
Excessive alcohol and smoking can affect general and reproductive health. Reducing alcohol and seeking support to stop smoking are more useful foundations than adding a “male vitality” blend. [4]
Supplements: separating a need from a marketing claim
Zinc
Zinc is involved in normal reproductive function. Food sources include meat, shellfish, dairy foods, legumes, nuts and seeds. Correcting deficiency is worthwhile, but extra zinc is not a reliable testosterone booster when intake is already sufficient.
Long-term high doses can cause copper deficiency and other problems. Check the combined amount if taking a multivitamin plus a separate male fertility or testosterone product. [5]
Vitamin D and magnesium
Vitamin D supports bone and muscle health. UK guidance is to consider 10 micrograms daily during autumn and winter, with year-round supplementation for some groups. This is different from taking high doses to raise testosterone, which is not an established treatment. [6]
Magnesium supports normal physiological function and is available from wholegrains, nuts, seeds, pulses and leafy vegetables. Supplements are not a proven general treatment for low testosterone. They can cause diarrhoea and require caution with kidney disease. [7]
Creatine and protein powders
Creatine may support performance in repeated high-intensity exercise and strength training. It is not a testosterone treatment. Protein powder can be a convenient food supplement where meals do not meet needs, but is not essential for everyone. [8]
Choose products for a specific purpose. If you have kidney disease or another relevant medical condition, discuss suitability before using sports supplements.
Herbal testosterone boosters and fertility antioxidants
Products containing tribulus, fenugreek, ashwagandha or multiple herbs are often marketed with promises that go beyond dependable clinical evidence. Product quality, medicine interactions and adverse effects also matter.
Antioxidant supplements are widely sold for sperm health, but evidence that they improve meaningful outcomes such as live birth is uncertain. The AUA/ASRM male infertility guideline describes the clinical utility of supplements as questionable and does not support a specific routine product. [4]
Avoid DHEA, prohormones and unregulated hormonal products without specialist medical advice. “Natural” does not mean that a product is safe or fertility-friendly.
Testosterone treatment and blood sugar
Testosterone therapy can be appropriate for confirmed hypogonadism after assessment of cause, benefits, risks and monitoring needs. It is not a general anti-ageing treatment, and the Endocrine Society recommends against prescribing it simply to improve glucose control in men with type 2 diabetes. [2]
Nutrition and lifestyle support can sit alongside necessary treatment. They cannot replace testosterone where there is a permanent medical deficiency, nor should medication replace attention to sleep, food and activity.
Taking the next step
Persistent sexual symptoms, unexplained fatigue, infertility or suspected diabetes deserve a medical review. Bring a list of medicines, supplements, sleep symptoms and any use of testosterone or anabolic steroids so that the assessment is complete.
I can support you with a food and lifestyle plan that fits your work, activity and health goals, while keeping appropriate medical investigation at the centre of persistent symptoms.
Related reading: How Blood Sugar Affects Your Hormones.
References and further reading
1. NIDDK. Insulin Resistance and Prediabetes.
2. Bhasin S et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. JCEM. 2018;103:1715–1744. doi:10.1210/jc.2018-00229.
3. NIDDK. Erectile Dysfunction.
4. AUA/ASRM. Diagnosis and Treatment of Infertility in Men.
5. NIH Office of Dietary Supplements. Zinc: Health Professional Fact Sheet.
6. NHS. Vitamin D.
7. NIH Office of Dietary Supplements. Magnesium: Health Professional Fact Sheet.
8. NIH Office of Dietary Supplements. Dietary Supplements for Exercise and Athletic Performance.
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