The surprising influence of female hormones on lab results

Blood tests which display levels of biomarkers – measurable units, such as cholesterol or glucose levels, that indicate the efficacy of biological functions – can help us understand the inner workings of our bodies to improve health, prevent disease, and understand the impact of lifestyle choices. 

One of the areas in which biomarkers have already made an impact is in personalized medicine. This modern approach to health is especially important for females. Many research studies and trials that helped develop successful treatments and surgeries were predominantly tested on male participants. 

Often, we don't know if these treatments are actually well-adapted to females. The only way to truly know is through a personalized approach. For a better understanding of female health, it’s essential to be aware that some blood tests can be different for each sex. 

Besides the fact that females have different reference ranges (expected ranges of values for a healthy population), female hormones can also influence lab results. Research shows that concentrations of various hormones fluctuating throughout the menstrual cycle may have significant effects on levels of biomarkers including iron, lipids, thyroid hormones, insulin, blood glucose, and more.

Blood tests which display levels of biomarkers – measurable units, such as cholesterol or glucose levels, that indicate the efficacy of biological functions – can help us understand the inner workings of our bodies to improve health, prevent disease, and understand the impact of lifestyle choices. 

One of the areas in which biomarkers have already made an impact is in personalized medicine. This modern approach to health is especially important for females. Many research studies and trials that helped develop successful treatments and surgeries were predominantly tested on male participants. 

Often, we don't know if these treatments are actually well-adapted to females. The only way to truly know is through a personalized approach. For a better understanding of female health, it’s essential to be aware that some blood tests can be different for each sex. 

Besides the fact that females have different reference ranges (expected ranges of values for a healthy population), female hormones can also influence lab results. Research shows that concentrations of various hormones fluctuating throughout the menstrual cycle may have significant effects on levels of biomarkers including iron, lipids, thyroid hormones, insulin, blood glucose, and more.

How your menstrual cycle works 

Your menstrual cycle affects many processes in your body. Throughout your cycle, your hormone levels rise and fall, affecting your blood test results. To understand how this works, it's essential to understand what goes on in your body during your menstrual cycle. 

Menstrual cycle phases

Your menstrual cycle happens in four phases. They are: 

• Menstruation: During menstruation, your uterus lining sheds and leaves your body through your vagina.
• Follicular phase: The follicular phase co-occurs with your menstruation. It begins on the first day of your period and ends when your ovulation begins. During this phase, your brain signals your pituitary gland to release the follicle-stimulating hormone (FSH). The hormone causes your ovaries to produce small follicles. Each follicle contains an immature egg and one egg will develop. 
• Ovulation: The egg developed during your follicular phase is released during ovulation. The luteinizing hormone (LH) stimulates this process. 
• Luteal phase: During this stage, the follicle that released your egg transforms into the corpus luteum, the function of which is to release progesterone. Progesterone helps keep the walls of your uterus thick and prepared for the implantation of a fertilized egg. You’re likely to experience PMS symptoms like mood swings, bloating, headaches, tender breasts, and food cravings during the luteal phase. 

If your egg isn’t fertilized during the luteal phase, your body absorbs it, your estrogen and progesterone levels drop, and your cycle starts all over again.

Your cycle and blood test results 

During each cycle, hormones are released at different times, which affects the way our bodies react to certain things. This can lead to different micronutrient biomarker concentrations and deficiencies in iron, magnesium, or zinc.

Iron 

Females with heavy periods tend to have lower iron levels. If you usually find yourself passing large blood clots, changing sanitary products multiple times in a day, or needing to use more than one type of sanitary product at a go, you likely have heavy periods. 

Not to worry – heavy periods are mostly nothing to worry about when they happen regularly instead of suddenly, but they do affect your iron levels. According to a 2013 study which cites older research from the World Health Organisation (WHO), about 10% of menstruating females lose around 1.4 milligrams of iron a day when they are on their period. 

In the same report, The WHO also estimates that you’re likely to lose an average of 80 ml of blood during your period. You’ll likely find that you have low iron levels when you do a blood test during or shortly after your period. Low iron levels over a prolonged period of time can lead to iron deficiency anemia which causes symptoms like fatigue, headaches, and dizziness.

If you notice any of these symptoms, speak to your doctor, who’s likely to recommend blood tests to make sure there are no other causes for your low Iron levels. If there are no other causes, a doctor is likely to prescribe iron supplements. 

You can also adjust your nutrition to iron-rich foods such as red meat and beans. Other biomarkers used to assess your iron levels include serum ferritin (SF), hemoglobin (Hb), soluble transferrin receptor (sTfR).

• Key insight: You’re likely to experience low iron levels during your period, especially if you have heavy periods. This is not necessarily indicative of an iron deficiency.
• Iron-rich foods: red meat, liver, nuts, and beans, are all healthy foods rich in iron. 

Lipids 

Lipids are fats found in your body responsible for regulating your body temperature, contributing to hormone synthesis, storing energy, and aiding digestion. They’re also an essential component of your tissues. They include cholesterol (HDL-cholesterol and LDL-cholesterol), phospholipids, and triglycerides. 

Your lipid levels fluctuate throughout your menstrual cycle because of your varying estrogen levels. Research shows that your total cholesterol and LDL-cholesterol levels are highest during the follicular phase of your cycle. 

In the luteal phase, these levels start to drop. As you ovulate, your HDL-cholesterol levels rise and peak on the day of your ovulation.  The varying levels of lipids throughout your cycle make it essential for your cycle to be taken into account when measuring cholesterol levels. 

• Key insight: Your lipid levels can be influenced by your menstrual cycle.
• Foods: When choosing fats in your diet, focus on healthy foods rich in unsaturated fatty acids. Healthy high-fat foods include avocados, salmon, tuna, nuts, eggs, and dark chocolate.

Vitamin D

Your body needs vitamin D to maintain healthy bones, regulate your immune system and maintain muscle function. Up to 50% of the world’s population has some degree of vitamin D deficiency. 

Your cycle also affects your vitamin D levels. Research shows that your vitamin D levels are highest during your period. Low vitamin D levels are common in females with PCOS or other conditions that cause irregular cycles and periods. 

Recent research has demonstrated a connection between vitamin D deficiency and frequent menstrual disorders, hence, Vitamin D supplements are thought by some to help regulate their periods and weight management.

During the luteal phase, there's a significant dip in your vitamin D levels which could be connected with PMS symptoms. Ensuring that your body is getting enough vitamin D can help you prevent PMS symptoms. Menopausal females are also likely to experience a dip in their vitamin D levels. 

• Key insight: Some research links menstrual disorder with low levels of vitamin D. It’s believed that vitamin D supplementation may help relieve symptoms. 
• Vitamin D-rich foods: Egg yolks, salmon, liver and red meat all contain vitamin D. However, vitamin D levels in food are typically low. If you’re worried about vitamin D deficiency, consider supplements after talking to your physician. 

C-reactive protein (CRP)

CRP is a biomarker used to check for signs of inflammation and infectious diseases. It can also be used to assess your chances of developing cardiovascular diseases. However, using CRP levels for these purposes can be complicated for females. 

When you’re on your period, your CRP levels are significantly higher than during other phases of your cycle.  Testing CRP levels during your period for a health assessment is likely to produce misleading results. Other factors affecting your CRP levels include hormonal birth control, blood pressure, and a high body mass index (BMI). 

• Key insight: Your CRP levels are at their highest during your period. Testing for the biomarker at this point may overestimate your typical levels. 
• Anti-inflammatory foods: A diet packed with olive oil, walnuts, berries and fatty fish can help lower your CRP levels. 

Magnesium deficiency and zinc

Zinc and magnesium are essential for several functions in your body. They help with energy production, boosting your immune system and cognitive function. During your period and the luteal phase of your cycle, you'll find that your zinc and magnesium levels are at their lowest. 

This means females have a higher chance of developing zinc and magnesium deficiencies. It's a good idea to ensure that foods rich in zinc and magnesium, such as green leafy vegetables, whole grains, beans, and nuts, are a regular part of your nutrition during this phase. 

• Key insight: You’re likely to experience low zinc and magnesium levels during your cycle's luteal and early follicular phases. Taking supplements and eating foods rich in both micronutrients can help cope with this and prevent a deficiency.
• Foods: The best food sources for magnesium and zinc include shellfish, pumpkin seeds, green leafy vegetables, beans, nuts and whole grains. 

Insulin sensitivity and blood glucose

Research shows that your insulin sensitivity likely varies throughout your menstrual cycle. Unfortunately, ongoing research into the prevention and treatment of insulin sensitivity often fails to consider the menstrual cycle. 

Females who have PMS are even more likely to experience varying insulin sensitivity during their cycle. A 2013 study compared the differences in insulin resistance and blood glucose in females with and without PMS and found that those with PMS had lower levels of blood glucose and insulin resistance than those without during their luteal phases.  

• Key insight: Research suggests that glucose levels and sensitivity to insulin may vary during the menstrual cycle, with stronger variations seen in females with PMS. 
• Foods for blood sugar balance: Foods such as carrots, cucumber, brown rice, salmon, and whole oats can help improve your insulin sensitivity. 

Thyroid hormones

Thyroid hormones are biomarkers used to check for endocrine conditions – conditions that affect the body’s hormone regulation – such as hypothyroidism, hyperthyroidism, and thyroiditis. They include the thyroid stimulating hormone (TSH), triiodothyronine (T3), and thyroxine (T4). 

TSH is an important biomarker. It is produced by the pituitary gland to stimulate the production of thyroid hormones. According to the U.S. Department of Health and Human Services, too much or too little thyroid hormone can make your periods very light, heavy, or irregular. 

If you’re pregnant, your T3 and T4 levels will increase in your first trimester while your TSH levels fall. They'll typically return to normal in your second trimester. Research shows that females are 5–8 times more likely to develop thyroid conditions, making accurate diagnosis when conducting tests with this biomarker even more crucial. 

Research also demonstrates that the time of day your blood is drawn can affect your blood test result. In a 2014 study, researchers found that their participants' thyroid hormone levels were much lower in the afternoon than in the morning. 

The study concluded that the best time to have blood drawn for this test is morning. Taking a blood sample in the afternoon instead of the morning was shown to possibly lead to a missed diagnosis of hypothyroidism in 50% of cases. 

• Key insight: Thyroid hormone levels are used to test for the possibility of thyroid-related conditions. Fluctuating levels of these hormones during your cycle can make testing in females a little more challenging. 
• Foods to balance your thyroid function: Eggs, salted nuts, roasted seaweed, and iodized salt have all been proven to help manage thyroid function. 

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