Hormones 101
An introduction to key hormones

Janine BSci BHSci(Nursing) PGCertPHC NZRN AUSRN

What are hormones?

Imagine a busy factory that produces toys day and night. Inside this factory are the factory’s supervisors (our hormones) who give instructions to the workers to complete important tasks to make sure everything runs perfectly. In the human body, hormones are powerful signals that instruct your body what to do and when to do it, just like the supervisors in the toy factory.

They do this by carrying messages through the bloodstream to your organs, muscles, and other parts of your body. Once they reach their destination, they help regulate your mood, metabolism (a food-power converter), and your growth and development. Examples of important hormones you will get to know briefly are oestrogen, progesterone, follicle stimulating hormone (FSH), luteinising hormone (LH), anti-mullerian hormone, thyroid stimulating hormone and testosterone.

Although there are many hormones in our body, we will cover them in subsequent articles.

Illustration by our founder & author, Janine for Mindful & Powerful Within., © 2025

But first, what is a hormonal imbalance?

To understand a hormonal imbalance, let’s return to our toy factory. A hormonal imbalance is when there are either too many or not enough supervisors, causing the factory to operate poorly. These supervisors either send too many or not enough messages to their workers (our organs or muscles). When this happens, the factory struggles to perform, leading to inefficiency, malfunctioning and sometimes, chaos. This is what a hormonal imbalance is.

In the human body, a hormonal imbalance can be short-term or long-term, causing significant bodily changes that can potentially lead to conditions that may require treatment. Some common examples you may have heard of include Polycystic Ovary Syndrome (PCOS), diabetes, and hypothyroidism (low thyroid hormone levels). These conditions will be discussed in subsequent articles.

Now, let’s talk about our first hormone: Oestrogen

Oestrogen acts like a chief architect in the factory. It is an important reproductive hormone found in both male and female systems. Known as one of the key female sex hormones, oestrogen plays a role in the development of the female reproductive system and the regulation of the menstrual cycle, as well as in bone strength, breast development, protection against cardiovascular disease, and pregnancy.

In the body, oestrogen is produced in special factory rooms called the ovaries, the adrenal glands, and even in the body’s fatty tissues (also known as adipose tissue).

Oestrogen levels can change throughout a woman’s life, especially during her menstrual cycle and with age. A significant decline in oestrogen levels during later life is called menopause.

There are three types of oestrogen, produced at different phases of a woman’s life

Oestradiol:

  • The main type of oestrogen in both males and females.

  • In females, it is primarily produced in the ovaries before menopause.

  • Excessive levels can lead to acne, loss of libido, and osteoporosis.

  • Extremely high levels have been researched to increase the risk of uterine and breast cancer.

  • Conversely, low levels of oestradiol are associated with a high risk of weight gain and cardiovascular disease.

Oestriol:

  • Produced by the placenta during pregnancy.

  • Levels peak just before birth.

  • Oestriol helps the uterus grow and prepares the body for delivery.

Oestrone:

  • This type of oestrogen is produced after menopause.

Illustration by our founder & author, Janine for Mindful & Powerful Within., © 2025

What Affects Oestrogen Levels?

Lifestyle, genetic, and medical factors can affect oestrogen levels. These include puberty, menopause, being overweight, strenuous exercise, certain medicines, and health conditions like diabetes or high blood pressure

Next up is Progesterone

  • Progesterone is a reproductive hormone primarily produced in the ovaries.

  • Other parts of the body, such as the adrenal glands and the placenta, also produce this hormone.

  • Progesterone plays a key role in regulating menstruation and preparing a part of the factory—the uterus, or "baby-growing room"—for pregnancy.

  • During pregnancy, progesterone levels increase to help thicken the lining of the uterus and prevent ovulation.

  • In males, the hormone helps in the production of sperm and other male hormones. Like oestrogen, progesterone levels begin to decline once menopause occurs.

LH and FSH

Luteinizing Hormone (LH) and Follicle-stimulating hormone (FSH) are crucial messengers that work as a team. They are both produced by the pituitary gland, a small gland the size of a kidney bean located at the base of the brain.

  • LH works with FSH to regulate the function of the testes in men and the ovaries in women.

  • In women, LH triggers the release of a mature egg from the ovary, a process known as ovulation.

  • In men, LH stimulates the production of testosterone.

  • FSH stimulates the growth of ovarian eggs inside the ovaries, supporting both ovulation and menstruation.

  • When we refer to the "follicles" in FSH, we are talking about ovarian follicles, which are the small sacs that contain the ovarian egg cells.

  • As ovarian function declines with age and the ovaries begin to produce fewer eggs, FSH levels rise.

  • During puberty, the pituitary gland produces more LH and FSH, which in turn stimulates the production of more oestrogen and progesterone.

AMH /Anti-Mullerian Hormone

AMH can be thought of as the factory's inventory manager.

  • It is a hormone produced by the cells within the ovarian follicles that house the ovarian eggs. AMH plays a crucial role in female reproductive health by corresponding to your ovarian reserve, or the number of eggs you have.

  • Higher AMH levels typically indicate a greater reserve of eggs, while lower levels suggest fewer eggs are available.

  • However, a high AMH level does not always guarantee a higher chance of natural fertility. Unlike some conditions, the symptoms of low AMH are not always obvious, but they may include an irregular menstrual cycle, heavy or light bleeding, fatigue, difficulty conceiving, and early menopause symptoms.

TSH / Thyroid-stimulating hormone

TSH acts as a key messenger from the master controller (the pituitary gland). Its job is to travel to a specific department in the factory—the thyroid gland—and tell it to start producing thyroid hormone.

  • This messenger regulates how much thyroid hormone your body produces. These thyroid hormones are essential because they affect your body’s use of energy and are important to nearly every part of your body.

  • They help regulate your heart, digestion, temperature, weight, brain development, mood, and metabolism.

  • High or low levels of TSH can significantly impact your health, and we will cover this in much more detail later.

TESTOSTERONE

  • Produced in both the testes of men and the ovaries of women, although it is present in much higher levels in men.

  • Responsible for stimulating the development of male characteristics

  • Plays a role in initiating the development of male reproductive organs during foetal development and is essential to produce sperm in adulthood.

  • Testosterone also signals the body to make new blood cells and ensures the factory’s structure – our muscles and bones - remain strong.

References

Cleveland Clinic. (2025). Estrogen. https://my.clevelandclinic.org/health/body/22353-estrogen

Cleveland Clinic. (2025). Thyroid-Stimulating Hormone (TSH) Levels. https://my.clevelandclinic.org/health/articles/23524-thyroid-stimulating-hormone-tsh-levels

Gowkielewicz M, Lipka A, Zdanowski W, Was´niewski T, Majewska M and Carlberg C (2024) Anti-Müllerian hormone: biology and role in endocrinology and cancers. Front. Endocrinol. 15:1468364. doi: 10.3389/fendo.2024.1468364

HealthDirect Australia Limited. (2025). Oestrogen. https://www.healthdirect.gov.au/oestrogen

Mitra, A. (2024). Dealing with Problem Periods. Headline Publishing Group

Stárka, L., & Dušková, M. (2020). What is a hormone?. Physiological research, 69(Suppl 2), S183–S185. https://doi.org/10.33549/physiolres.934509

The Johns Hopkins University. (2025). Hormones and the Endocrine System. https://www.hopkinsmedicine.org/health/conditions-and-diseases/hormones-and-the-endocrine-system