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a type of sex steroid hormone found in men and women responsible for secondary sexual characteristics. There are three oestrogens – oestrone, oestradiol and oestriol – the most potent of which is oestradiol.

Oestrone is a hormone produced by the ovaries. It is one of the major oestrogens in postmenopausal women.

Hormones in the News: Oestrogen
Highly commended runner-up: Daniel Foran, Imperial College London

What is HRT?
Hormone replacement therapy (or HRT) is the replacement of female sex hormones oestrogen and progesterone in women to control symptoms of the menopause.

Androstenedione is a steroid hormone that has weak, androgenic actions on the body itself. However, it mainly acts as a stepping stone in the manufacture of testosterone and oestrogen within the body.

The ovaries produce and release eggs (oocytes) into the female reproductive tract at the mid-point of each menstrual cycle. They also produce the female hormones oestrogen and progesterone.

Polycystic ovary syndrome
Polycystic ovary syndrome is a term that covers a spectrum of problems caused by an imbalance in the level of the body's sex hormones (oestrogen and testosterone).

corpus luteum

a temporary endocrine gland formed from the ruptured ovarian follicle (which enclosed the egg) after an egg is released at ovulation. The corpus luteum produces the hormones progesterone and oestradiol (an oestrogen).

contraceptive pill

a hormone drug taken by women to prevent ovulation and therefore to stop a pregnancy occurring (contraception). There are several different types of pill; the ‘combined’ pill contains oestrogen and progesterone; the ‘mini’ pill contains progesterone-only.

Hormones in human reproduction
Hormones are the drivers of human reproduction, responsible for sexual development and controlling the menstrual cycle.

Hormones of pregnancy and labour
This article describes hormones that play an important role in pregnancy and labour.

Gonadotrophin-releasing hormone
Gonadotrophin-releasing hormone is released from nerve cells in the brain. It controls the production of luteinising hormone and follicle stimulating hormone from the pituitary gland.

Delayed puberty
Delayed puberty is defined as no secondary sexual maturation or any sign of puberty by the age of 13 years in girls and 14 years in boys.

The menopause is the time when menstruation stops because the ovaries stop producing hormones and releasing eggs for fertilisation. This marks the end of a woman's reproductive years.

Osteoporosis is a bone disorder caused by loss of bone mass, resulting in abnormal bone structure and an increased risk of fracture.

Endometrial cancer
Endometrial cancer is a form of cancer that originates from the tissue that lines the womb. This tissue is called the endometrium.

Premature ovarian failure
The period between puberty and the menopause represents the reproductive window of most women. If the ovaries stop working prematurely (roughly before the age of 40) and there are subsequently no periods, this is called premature ovarian failure.

Dehydroepiandrosterone is an important precursor hormone, and is the most abundant circulating steroid present in the human body. It has little biological effect on its own but has powerful effects when converted into other hormones such as sex steroids.

Oestriol is a hormone made during pregnancy that can be used to measure fetal health and predict when birth may happen.

Prolactin is a hormone produced in the pituitary gland, named because of its role in lactation. It also has other wide ranging functions in the body, from acting on the reproductive system to influencing behaviour and regulating the immune system.

Oestradiol is a powerful reproductive hormone that has a wide range of actions in both men and women.

The placenta is a temporary endocrine organ formed during pregnancy, which produces hormones important in the maintenance of a healthy pregnancy and in preparation for labour and breastfeeding.

Winners of 2020 Student Video Award
Bringing endocrinology to life

Follicle stimulating hormone
Follicle stimulating hormone is produced by the pituitary gland. It regulates the functions of both the ovaries and testes. Lack or insufficiency of it can cause infertility or subfertility both in men and women.

Turner syndrome
Turner syndrome is a chromosomal disorder affecting the equivalent of one in 2,500 girls, which may lead to a number of features including short stature, failure to enter puberty and infertility.

Endometriosis is a condition in women where the lining of the womb grows outside of the womb causing scar tissue and painful monthly periods.

Sheehan's syndrome
Sheehan's syndrome is a rare condition affecting the pituitary gland that occurs as a result of heavy bleeding during or after childbirth.

Amenorrhoea is the term used to describe a lack of 'periods' (menstrual cycles) in women. The management of amenorrhoea depends on the underlying cause.

Luteinising hormone
Luteinising hormone is produced by the pituitary gland and is one of the main hormones that control the reproductive system.

Premenstrual syndrome
Premenstrual syndrome (PMS) is a condition that affects women during the days leading up to her monthly period; it can cause distressing physical and emotional symptoms.

Angiotensin is a protein hormone that causes blood vessels to become narrower. It helps to maintain blood pressure and fluid balance in the body.

The menstrual cycle
The menstrual cycle is governed by an interaction between reproductive hormones which prepares the endometrium (or womb) for pregnancy, or if no pregnancy occurs, the fall in progesterone leads to shedding of the endometrial lining and recommences the monthly cycle.

Gender identity disorder
Gender identity disorder is where a person is deeply unhappy with the gender they were born in, because it is different from the gender they feel they should be. This often leads to a desire to live in their preferred gender and change their appearance.

Hirsutism is the presence of excess male-pattern hair growth in women and is commonly caused by an imbalance of hormones.

Progesterone is a hormone released by the corpus luteum in the ovary. It plays important roles in the menstrual cycle and in maintaining the early stages of pregnancy. It may also be involved in the growth of certain cancers.

Precocious puberty
Precocious puberty is the abnormally early development of any secondary sexual characteristics: before the age of nine years in a boy and eight years of age in a girl.

Hormones and conservation
The study of animal reproductive systems and regular monitoring of reproductive and stress hormones is important for conservation.

Are everyday chemicals harming my health?
There are chemicals all around us, but can they interfere with our hormones? Endocrine disruptors have been linked with a number of health problems, so for the final episode in the series we look at where these chemicals are found and whether we should be worried.

Nelson's syndrome
Nelson's syndrome is the name given to the enlargement of a pituitary gland tumour associated with excess secretion of adrenocorticotropic hormone following the surgical removal of both adrenal glands, usually to treat Cushing's disease.

Animal research in science
The controlled and regulated use of laboratory animals in medical research has helped to extend our understanding of the healthy and diseased lifecourse, as well as the development of novel and effective therapeutic interventions.

Addison's disease
Addison's disease is caused by damage to the adrenal glands, which make hormones to control multiple metabolic processes in the body, and balance body salt and water. Treatment is with hormone replacement tablets and some lifestyle adaptations to ensure patients remain well.

Hypoparathyroidism is a rare condition characterised by inadequate parathyroid hormone production from the parathyroid glands, resulting in low calcium levels in the bloodstream.

Gigantism is a rare condition due to abnormal, accelerated growth caused by excessive amounts of growth hormone secretion during childhood or adolescence. It is almost always the result of a growth hormone-secreting pituitary tumour.

Eating disorders
Eating disorders refer to unhealthy eating habits, which cause psychological and physical damage but can be treated in many cases.

Growth and height
The height a person reaches as an adult is a result of their genes as well as general health and nutrition during their years of growth. Normal growth is controlled by hormones such as growth hormone, sex hormones and thyroid hormones.

In vitro fertilisation treatment (IVF)
In vitro fertilisation is a fertility treatment which stimulates the ovaries to produce multiple eggs which are collected and fertilised by sperm outside of the body in the laboratory to create embryos. One or two of which are then selected and transferred back to the womb in order to result in pregnancy.

Prader-Willi syndrome
Prader-Willi syndrome is a genetic disorder leading to excess hunger and obesity, lack of some hormones, developmental delay, learning difficulties and behavioural problems.

Diabetes mellitus
Diabetes mellitus is a very common disorder caused by high levels of sugar in the bloodstream. It affects a large number of people, with many more people remaining undiagnosed.

Insulin is an essential hormone produced by the pancreas. Its main role is to control glucose levels in our bodies.

Multiple endocrine neoplasia type 1
Multiple endocrine neoplasia type 1 is a rare inherited disease, which can result in tumours in the pituitary and parathyroid glands, and pancreas.

Goitre is a general term for an enlarged thyroid gland. Depending on the type of swelling, location, how it affects gland function and how long it has been present, goitre has various effects and is treated in a variety of different ways.

Hypothyroidism is a condition that develops when the thyroid gland is unable to produce enough thyroid hormones.