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How Hormonal Birth Control Affects Thyroid Function

How does the OCP, (Oral Contraception Pill), affect a woman’s thyroid function??

This is a question that needs to be answered and much more research done in this area.

How many women have been prescribed the OCP from an early age go on to develop a thyroid condition?

It is not the only nuance that can trigger thyroid dysfunction, but hormonal birth control, needs to be taken into consideration as a possible contributing factor.

Let’s look at the big picture here….

All hormones are connected

All of the hormones within the entire endocrine system are connected.

We need adequate progesterone to be able to utilise thyroid hormones at a cellular level. Progesterone is not the same as the synthetic Progestin which is used in hormone birth control, so how does this affect thyroid hormone synthesis and cellular uptake?? Not a lot of research has ben done in this area, but that does not mean that that there is an absence of safety here.

Switching Off Brain Function

The OCP uses large doses of synthetic hormones to shut down the body’s natural hormone cycles to prevent ovulation and pregnancy. It does this by working at a brain level. The large doses of hormones communicate with the brain to shut down the pituitary’s communication with the ovaries. The Pituitary is also the same part of the brain where TSH, (thyroid Stimulating Hormone), comes from. TSH communicates with the thyroid to tell the thyroid to produce more or less thyroid hormones, depending on what certain cells and tissues in the body needs. If the OCP shuts down the brain communication, this will affect thyroid function also, often presenting as a low TSH.

The OCP affects Cortisol

The OCP also affects cortisol by again affecting the brains communication system by shutting down the HPA (Hypothalamic, Pituitary, Adrenal axis), our stress and nervous systems major feedback loop. HPA dysregulation affects thyroid hormone production. When we track a woman’s cortisol and HPA function when they are on the OCP, it looks like they have had a chronic stress for a long time. Women often report a low stress response or low stress resilience with OCP uses. Healthy adrenal function is vital for healthy thyroid function.

Hormonal induced nutrient deficiencies

The OCP depletes key nutrients – this is widely researched and documented. Nutrients such as selenium, zinc, Vitamin A, and iodine are all depleted by the OCP. These nutrients are all needed for thyroid hormone production, utilisation and conversion in the body.

The OCP affects the liver

Any synthetic medication has to be metabolised by the liver and also large doses of hormones such as in the OCP all have to be metabolised by the liver. The thyroid hormone T4 is converted to its active form T3 in the liver. If the liver is compromised by excess hormones, this affects thyroid hormone conversion. This will present as normal T4 levels but low levels of T3 causing symptoms such as weight gain, fatigue and brain fog.

Poor Gut Health

The OCP affects the gut by increasing intestinal permeability or leaky gut. Thyroid hormone conversion is also affected by leaky gut, causing low levels of T3. We need good levels of T3 to produce HCL, (hydrochloric acid), in the stomach. We need HCL to digest and absorb the food we eat. It is an essential ingredient for digestion. Low HCL is a common deficiency in my thyroid clients. Healthy gut function is essential good for healthy thyroid function.

All these issues – nutrient deficiencies caused by the OCP, poor liver and gut conversion to the active thyroid hormones the body can use, causing low levels of T3 needed to produce HCL in the gut which further depletes nutrients, and increases intestinal permeability and dysbiosis in the gut …which is a vicious cycle!!

Binding proteins

When there are high levels of hormones in the blood stream, such as with OCP use, the body produces SHBG, (Sex Hormone Binding Globulin), a binding protein, as a protective mechanism to save guard against excess hormones. SHBG is often high with OCP use. SHBG also binds excess testosterone which is why the OCP is used to treat acne caused by high levels of testosterone. SHBG will also grab onto thyroid hormones such as T4 so the body can’t utilise the thyroid hormones as it is bound. This can often be a reason when your T4 looks ok in a blood test but you still experience thyroid symptoms. The test is picking up on the bound amount and not what is getting into the cells.


Another marker we can measure when a woman is on the OCP is CRP, (C Reactive protein), which is a marker of inflammation. The OCP is known to increase inflammation in the body. When a woman is inflamed, apart from increasing her cardiovascular risk, inflammation affects how the cells take up hormones. Inflammation blocks the conversion of T4 to T3 in the peripheral tissues. Another effect of inflammation is Insulin Resistance or poor blood sugar control in the body. IR is another common driver, cause, trigger of thyroid dysfunction.

Hypothyroidism and Hashimotios can cause period irregularities

So many women go to their GP for period or menstrual irregularities which can be caused by poor thyroid function. If a woman is put on the OCP, to regulate their period, often the underlying thyroid condition is not identified and then as we have outlined above, their thyroid condition often get's worse with OCP use.

There are so many ways in which hormonal birth control can affect thyroid function. It is a factor to consider in any thyroid condition. If you choose to use the OCP and other hormonal birth control then please monitor your thyroid health and nutritional deficiencies. Natural therapies can support this choice or offer safer options.

Get in touch today for more information.


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