How Blood Sugar Affects Your Hormones

‍How Blood Sugar Affects Your Hormones: The Connection Between Insulin, Oestrogen, Testosterone, Stress and Thyroid Health

When we think about hormones, it is easy to think about them individually.

Perhaps you have been told that your oestrogen is too high, your testosterone is low, your thyroid isn’t working properly, or that stress is affecting your cortisol.

But hormones don’t work in isolation.

They are part of a complex communication network known as the endocrine system, with different hormones constantly influencing one another.

One of the most important influences on this system is something we don’t always think of as being connected to hormones at all: blood sugar regulation.

Blood sugar, insulin, sex hormones, cortisol and thyroid hormones are all interconnected. This means that problems in one area can sometimes have consequences elsewhere.

Whether you are experiencing fluctuating energy, changes in weight, PMS, acne, changes in libido, poor sleep or difficulty maintaining stable energy throughout the day, understanding this relationship can be useful.

Let’s look at how it all fits together.

The Endocrine System – Everything Is Connected

The endocrine system is made up of glands and tissues throughout the body that produce hormones.

Hormones are chemical messengers that travel through the bloodstream and influence processes including:

• metabolism
• reproduction
• energy production
• appetite
• sleep
• growth
• stress responses
• mood
• sexual function.

Some of the key players include:

• the pancreas
• the thyroid gland
• the adrenal glands
• the ovaries
• the testes
• the pituitary gland
• the hypothalamus.

These systems are constantly communicating.

For example, insulin can influence sex hormone availability, sex hormones can affect the proteins that transport thyroid hormones, and cortisol can influence blood glucose.

This interconnectedness is why looking at one hormone in isolation doesn’t always tell the whole story.

The Pancreas – Your Blood Sugar Regulator

Every time you eat carbohydrate-containing foods, they are broken down into glucose, which enters your bloodstream.

Your pancreas responds by releasing insulin.

Insulin helps glucose move from the bloodstream into your muscles, liver and other tissues, where it can be used for energy or stored for later.

This is a normal and essential process.

Problems can arise when blood glucose and insulin remain elevated repeatedly over a prolonged period.

The cells can gradually become less responsive to insulin’s signal. This is known as insulin resistance.

To compensate, the pancreas produces more insulin in an attempt to keep blood glucose within a healthy range.

For a while, blood glucose may still appear normal because the pancreas is successfully compensating. However, persistent insulin resistance can place increasing demands on the insulin-producing beta cells of the pancreas.

In some people, the pancreas eventually cannot produce enough insulin to compensate, contributing to impaired glucose regulation and potentially Type 2 diabetes. (Endocrine Society⁠)

Insulin resistance is also an important feature of metabolic syndrome and is associated with increased cardiovascular risk.

But insulin doesn’t only regulate blood sugar.

It also interacts with the reproductive hormones.

Blood Sugar and Female Hormones

The relationship between insulin and female hormones is particularly interesting.

Insulin and SHBG

One of insulin’s effects is on a protein made by the liver called sex hormone-binding globulin (SHBG).

SHBG binds to hormones such as oestrogen and testosterone in the bloodstream and helps regulate how much remains freely available to tissues.

When insulin levels remain elevated for prolonged periods, SHBG production can be reduced, particularly in the context of insulin resistance.

Lower SHBG can mean that a greater proportion of circulating sex hormones remains unbound and biologically active.

This doesn’t necessarily mean that the body is producing more oestrogen. Instead, it changes the balance between bound and unbound hormone.

This relationship can be particularly relevant in conditions such as polycystic ovary syndrome (PCOS).

Insulin, Androgens and Ovulation

Insulin can also influence the ovaries directly.

Persistently elevated insulin can stimulate ovarian production of androgens, including testosterone.

This is particularly well established in PCOS, where insulin resistance, elevated androgens and disrupted ovulation commonly occur together.

Higher androgen levels can interfere with normal follicle development and ovulation.

If ovulation doesn’t occur regularly, progesterone production may also be reduced because progesterone is produced predominantly after ovulation.

This can contribute to irregular cycles and a relative imbalance between oestrogen and progesterone.

Blood Sugar and Male Hormones

Blood sugar and insulin are also closely connected with male reproductive hormones.

The primary male sex hormone is testosterone, although men also produce oestrogen, progesterone and other steroid hormones in smaller quantities.

Testosterone is important for:

• libido
• sperm production
• muscle mass
• bone health
• red blood cell production
• energy and wellbeing
• sexual function.

Research has found an association between insulin resistance, obesity, lower SHBG and lower testosterone in men. Low SHBG is frequently seen alongside metabolic dysfunction, and testosterone levels can also be lower in men with Type 2 diabetes. (OUP Academic⁠)

The relationship is not simply a case of “high insulin causes low testosterone”, however.

It is bidirectional and influenced by several factors, including body composition, insulin sensitivity, SHBG, age, sleep, illness, medications and the function of the hypothalamic-pituitary-gonadal (HPG) axis.

This is important because testosterone results should always be interpreted in context.

For example, a man’s total testosterone and free testosterone can tell different stories depending on his SHBG level.

The Endocrine Society recommends that a diagnosis of testosterone deficiency should be based on compatible symptoms together with consistently low testosterone confirmed by appropriate morning blood testing, rather than symptoms alone. (PubMed⁠)

Testosterone and Body Fat

Body composition also matters.

Higher levels of visceral and abdominal fat are associated with insulin resistance and lower SHBG and testosterone levels.

This creates an interesting cycle:

More visceral fat → greater insulin resistance → altered SHBG and testosterone → potentially less favourable body composition and metabolic health.

This doesn’t mean that testosterone is simply a “fat-burning hormone”, nor that increasing testosterone will automatically cause weight loss.

Rather, metabolic health, body composition and reproductive hormones are interconnected.

Improving insulin sensitivity through nutrition, physical activity, resistance training, sleep and gradual improvements in body composition can therefore be an important part of supporting healthy testosterone levels.

Oestrogen Isn’t Just a Female Hormone

It is also important to remember that men produce oestrogen too.

Testosterone can be converted into oestradiol, the main form of oestrogen in both men and women, by an enzyme called aromatase.

In men, oestrogen plays an important role in:

• bone health
• sexual function
• libido
• cardiovascular and metabolic health.

So the aim isn’t to eliminate oestrogen in men or women.

Hormone health is about having an appropriate balance and regulation of hormones for the individual.

The Thyroid Connection

The thyroid gland produces hormones that regulate metabolism, energy production, body temperature and many other processes.

The two main thyroid hormones are:

• T4 (thyroxine)
• T3 (triiodothyronine) – the more biologically active thyroid hormone.

Oestrogen and thyroid hormones have a close relationship.

Oestrogen stimulates the liver to produce thyroxine-binding globulin (TBG), a protein that transports thyroid hormones through the bloodstream.

When TBG increases, more thyroid hormone becomes bound to it, temporarily reducing the amount of free hormone available.

A healthy thyroid can generally compensate by producing more hormone. However, in someone with an underlying thyroid condition or reduced thyroid reserve, changes in TBG can sometimes affect thyroid hormone availability.

This can be particularly relevant during pregnancy or when taking oral oestrogen-containing medication.

It would be an oversimplification to say that high oestrogen directly causes an underactive thyroid. Thyroid disorders have many possible causes, including autoimmune thyroid disease, iodine imbalance and other factors.

Your Stress Response – The HPA Axis

The adrenal glands sit above the kidneys and produce several important hormones, including:

• cortisol
• adrenaline
• noradrenaline
• aldosterone
• DHEA.

When you experience physical or emotional stress, illness, intense exercise, insufficient food or significant low blood glucose, your body activates its stress response.

One of the main systems involved is the hypothalamic-pituitary-adrenal (HPA) axis.

It works as a communication chain:

1. The hypothalamus releases corticotropin-releasing hormone (CRH).
2. CRH signals the pituitary gland to release ACTH.
3. ACTH signals the adrenal glands to produce cortisol.

Cortisol is an essential hormone.

It helps the body:

• maintain blood glucose
• stimulate glucose production by the liver
• regulate inflammation
• respond to physical and psychological stress
• support blood pressure and circulation.

When blood glucose falls too low, cortisol works alongside glucagon and adrenaline to help restore it.

When Stress Becomes Long-Term

The stress response is designed to be temporary.

However, ongoing psychological stress, poor sleep, illness, repeated blood sugar fluctuations or excessive physical demands can influence the normal regulation and rhythm of cortisol.

Rather than the adrenal glands simply becoming “exhausted”, research describes changes in the regulation of the HPA axis in response to chronic stress.

This is sometimes referred to as HPA-axis dysregulation.

It is important to distinguish this from “adrenal fatigue”. Adrenal fatigue is not a recognised medical diagnosis and there is no good evidence that the adrenal glands become exhausted from everyday psychological stress. (Endocrine Society⁠)

Some people experiencing chronic stress may nevertheless have altered cortisol patterns and symptoms such as:

• fatigue
• disturbed sleep
• difficulty coping with stress
• anxiety
• changes in appetite
• increased cravings
• reduced concentration
• changes in exercise recovery.

These symptoms are non-specific and can have many causes, so they shouldn’t automatically be attributed to HPA-axis dysfunction.

There is also a genuine medical condition called adrenal insufficiency, where the body cannot produce enough cortisol. This is very different from stress-related changes and requires appropriate medical assessment. (Endocrine Society⁠)

Cortisol and Thyroid Hormones

Stress hormones can also influence thyroid hormone metabolism.

During prolonged physiological stress or illness, changes in cortisol and other signalling pathways can affect the conversion of T4 into T3.

T4 is converted into T3 by enzymes called deiodinases. During significant illness or physiological stress, thyroid hormone metabolism can change.

The liver and gastrointestinal tract also have important roles in thyroid hormone metabolism, making adequate nutrition and overall health relevant to thyroid function.

Blood Sugar and Sleep

Have you ever fallen asleep easily only to wake in the early hours feeling wide awake?

Blood sugar is one possible piece of the puzzle.

If blood glucose falls significantly during the night, the body has mechanisms to protect the brain and restore glucose levels. Counter-regulatory hormones including glucagon, adrenaline and cortisol can be released.

For some people, this may contribute to waking, increased heart rate or a feeling of anxiety.

However, blood sugar isn’t the only reason people wake during the night.

Other possibilities include:

• menopause and perimenopause
• stress
• alcohol
• sleep apnoea
• medication
• pain
• needing to use the bathroom
• environmental disturbances.

During the day, blood sugar fluctuations may show up as:

• feeling “hangry”
• shakiness
• brain fog
• afternoon energy crashes
• strong cravings for sweet foods
• feeling tired after eating
• relying heavily on caffeine.

These symptoms aren’t proof of blood sugar problems, but they can be useful clues to consider alongside the wider picture.

What Does the Body Need to Make Hormones?

Nutrition provides many of the raw materials and cofactors involved in hormone production, metabolism and signalling.

This doesn’t mean that eating a particular food will automatically increase or decrease a specific hormone. Hormone production is tightly regulated by the body.

However, consistently inadequate nutrition can make it harder for the body to carry out these processes effectively.

Protein

Protein provides amino acids needed for enzymes, receptors, transport proteins and many other components involved in hormone signalling.

Adequate protein is also important for maintaining muscle mass, which plays an important role in glucose regulation.

Sources include:

• eggs
• fish
• meat
• poultry
• Greek yoghurt
• tofu
• tempeh
• beans
• lentils
• nuts and seeds.

Fats and Cholesterol

Oestrogen, progesterone, testosterone and cortisol are all steroid hormones.

Cholesterol provides the starting material from which steroid hormones are made. (OUP Academic⁠)

This doesn’t mean that eating large quantities of cholesterol will automatically increase testosterone or oestrogen. The body produces and regulates cholesterol itself, and hormone production involves multiple steps and enzymes.

Adequate dietary fat is nevertheless important as part of a balanced diet.

Good sources include:

• extra virgin olive oil
• avocado
• nuts
• seeds
• oily fish
• eggs.

Vitamins and Minerals

Hormone production and metabolism also depend on a wide range of vitamins and minerals.

These include nutrients such as:

• magnesium
• zinc
• selenium
• iodine
• vitamin D
• B vitamins
• vitamin C.

Zinc, for example, is important for normal reproductive function, and zinc deficiency has been associated with lower testosterone levels. However, supplementation does not necessarily increase testosterone in someone who already has adequate zinc status. (ScienceDirect⁠)

Vitamin D has also been investigated in relation to male hormones. Some recent evidence suggests supplementation may increase total testosterone in men, but effects on free testosterone and other reproductive hormone markers are much less consistent. (PubMed⁠)

This is a good example of why correcting a deficiency is different from taking high-dose supplements in the hope of “boosting” hormones.

Supporting Blood Sugar Balance Naturally

The good news is that supporting blood sugar doesn’t require eliminating carbohydrates or following an extremely restrictive diet.

Instead, think about how you combine foods.

Include Protein at Meals

Protein helps with satiety and can support a steadier post-meal blood glucose response.

Try adding eggs, Greek yoghurt, tofu, fish, chicken, beans or lentils to meals rather than having a carbohydrate-only breakfast.

Instead of:

Toast and jam

Try:

Wholegrain toast with eggs and avocado.

The second meal provides protein, fat and fibre alongside carbohydrate.

Choose Fibre-Rich Carbohydrates

Carbohydrates aren’t the enemy.

Your brain and muscles use glucose for energy, and carbohydrate-containing foods can provide valuable fibre, vitamins, minerals and phytonutrients.

Choose foods such as:

• vegetables
• fruit
• beans
• lentils
• chickpeas
• oats
• wholegrains
• potatoes
• sweet potatoes.

Fibre slows digestion and helps regulate the release of glucose into the bloodstream.

It also provides food for beneficial gut bacteria, which produce short-chain fatty acids that can influence metabolic health.

Include Healthy Fats

Healthy fats can help slow gastric emptying and are important for cell membranes, absorption of fat-soluble vitamins and the production of steroid hormones.

Good choices include olive oil, avocado, nuts, seeds and oily fish.

Think About the Whole Meal

Rather than worrying about whether an individual food is “good” or “bad” for blood sugar, think about the whole meal.

A useful template is:

Protein + fibre-rich carbohydrate + vegetables + healthy fat

For example:

Salmon + new potatoes + broccoli + olive oil

or

Lentil dhal + brown rice + vegetables + natural yoghurt

or

Eggs + wholegrain toast + avocado + tomatoes

This combination provides protein, carbohydrate, fibre and healthy fats together.

Movement Matters Too

Exercise is another powerful tool for blood sugar regulation.

When muscles contract, they can take up glucose from the bloodstream, helping to reduce blood glucose levels.

Regular physical activity improves insulin sensitivity, meaning the body can respond more effectively to insulin.

Walking after meals, resistance training, yoga, cycling, swimming or any other enjoyable movement can all contribute to metabolic health.

Resistance exercise is particularly valuable because maintaining and building muscle provides the body with a larger reservoir for glucose disposal.

This is relevant to both men and women, particularly as we get older and naturally begin to lose muscle mass.

Sleep and Stress Matter

Nutrition is only one part of the picture.

Poor sleep can affect appetite, insulin sensitivity and the hormones involved in hunger and fullness.

Likewise, chronic stress can influence cortisol, appetite, blood glucose and food choices.

This is why supporting hormone health isn’t simply about eating the “perfect” diet.

It is also about creating the conditions in which your body can regulate itself.

That might mean:

• establishing a consistent sleep routine
• getting daylight exposure during the morning
• taking regular breaks
• practising yoga or breathwork
• spending time outdoors
• walking regularly
• including enjoyable movement
• making time for relaxation
• avoiding excessive dietary restriction or over-exercising.

Bringing It All Together

Hormones don’t work in isolation.

Insulin, oestrogen, progesterone, testosterone, cortisol and thyroid hormones are all part of an interconnected system.

Blood sugar regulation sits at the centre of many of these relationships.

Persistent insulin resistance can influence sex hormone availability and reproductive function in both women and men. Stress hormones can influence blood glucose and thyroid hormone metabolism, while adequate nutrition provides the building blocks and cofactors required for hormone production.

The aim isn’t to “balance” one hormone by following a rigid diet or taking a long list of supplements.

Instead, think about creating the right environment for your endocrine system to function well.

That means eating nourishing, balanced meals, supporting your gut, maintaining muscle, moving your body, getting enough sleep and finding ways to manage the inevitable stresses of life.

Small, consistent changes are often more valuable than trying to achieve perfection.

And if you’re experiencing persistent symptoms such as fatigue, significant changes in weight, irregular periods, acne, reduced libido, erectile difficulties, poor sleep or other hormone-related concerns, it’s important to look at the whole picture rather than assuming one hormone is responsible.

Hormone health is complex – but understanding the connections can be a useful first step.

Topics Included

• Blood sugar regulation
• Insulin and insulin resistance
• Metabolic health
• Sex hormone-binding globulin (SHBG)
• Oestrogen and progesterone
• Insulin and female reproductive hormones
• PCOS and insulin resistance
• Testosterone and male hormone health
• Testosterone, insulin resistance and metabolic health
• SHBG and testosterone in men
• Oestrogen in men
• Thyroid hormones and TBG
• Cortisol and the stress response
• The HPA axis
• HPA-axis dysregulation
• Blood sugar and sleep
• Nutrition and hormone production
• Protein and hormone health
• Dietary fats and steroid hormones
• Cholesterol and hormone production
• Zinc, selenium, iodine and vitamin D
• Fibre and the gut microbiome
• Exercise and insulin sensitivity
• Resistance training and muscle health
• Sleep, stress and metabolic health

References & Further Reading

Endocrine Society – Sex Hormones and Diabetes

Research exploring relationships between sex hormones, SHBG, testosterone and glucose metabolism. (Endocrine Society⁠)

Endocrine Society – Testosterone Therapy in Men With Hypogonadism

Clinical guidance on assessing testosterone deficiency, including the importance of symptoms, repeated morning testosterone measurements and consideration of SHBG/free testosterone. (OUP Academic⁠)

Endocrine Society – Adrenal Fatigue

An explanation of why “adrenal fatigue” is not recognised as a medical diagnosis and why other causes of fatigue should be investigated. (Endocrine Society⁠)

Endocrine Society – Adrenal Insufficiency

Information about genuine adrenal insufficiency and how it differs from the concept of adrenal fatigue. (Endocrine Society⁠)

Endocrine Society – Adrenal Hormones

Background information on cortisol, adrenaline and other adrenal hormones and their roles in metabolism and the stress response. (Endocrine Society⁠)

Journal of the Endocrine Society – Pseudo-Endocrine Disorders: Recognition, Management, and Action

A 2025 review discussing unsupported endocrine concepts, including adrenal fatigue, and the importance of distinguishing these from genuine endocrine disorders. (Endocrine Society⁠)

Journal of Clinical Endocrinology & Metabolism – Sex Steroid Hormones, Obesity and Insulin Resistance

Research examining the relationship between obesity, insulin resistance, SHBG and testosterone in men. (PubMed⁠)

Endocrinology – Cholesterol and Steroid Hormone Synthesis

Background on cholesterol as the precursor for steroid hormone production. (OUP Academic⁠)

Journal of Trace Elements in Medicine and Biology – Zinc and Testosterone

Systematic review examining the relationship between zinc status and testosterone. (ScienceDirect⁠)

PubMed – Vitamin D and Androgens in Adult Men

Systematic review and meta-analysis examining vitamin D supplementation and testosterone-related markers in men. (PubMed⁠)

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What is the difference between a; dietitian, nutritionist and nutritional therapist.

Dietitian's - Dietitian's provide practical guidance to sick individuals to help them  make appropriate, healthy choices for a specific medical conditions. They often work as part of a clinical team, including for example doctors, nurses, physiotherapists etc. They take a direct approach to the illness being presented to them, not the body as a whole.

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