(2) Examples of hormones and which gland or organ produces them

Hormones are produced in, and secreted by, various glands called endocrine glands - hence the overall description - the endocrine system - sources and examples of which are described below.

Endocrine glands secrete hormones directly into the bloodstream.

 

Pituitary gland

The pituitary is a small gland at the base of the brain

The pituitary gland produces many hormones that regulate conditions in the body and growth hormone is important for the development of the body.

Some hormones have a direct effect on the body, but others have an indirect effect by causing other glands to release hormones.

Which is why the pituitary gland is sometimes referred to as the master gland because these hormones act on other glands causing them to release other hormones to bring about changes somewhere in the body.

The pituitary gland produces the hormones FSH and LH which are important control chemicals in the female menstrual cycle. These act on the ovaries and testes to release reproductive hormones which control the release of eggs from the ovaries and the birth of a baby.

FSH = Follicle stimulating hormone   and   LH = Luteinizing hormone

The pituitary gland secretes the hormone TSH which acts on the thyroid gland - which in turn secretes thyroxine hormone (see next section).

TSH = Thyroid stimulating hormone

It also produces the hormone ACTH which acts on the adrenal gland to secrete the hormone adrenal hormone.

ACTH = Adrenocorticotropic hormone

The pituitary produces the growth hormone STH, which acts on the whole body - if very deficient in STH for a long time you may be of short stature and dwarfism, and, if too much of STH for a long time you have excessive growth in stature, organ enlargement and suffer from functional disorders such as diabetes and heart disease.

STH = somatotropin or somatotropic hormone

ADH is a hormone that is produced in a part of the brain called the hypothalamus. It is then stored and released from the pituitary gland. ADH acts on the kidneys to control the amount of water excreted in the urine.

ADH = Anti-diuretic hormone

See Homeostasis - osmoregulation, ADH, water control and kidney function

 

Thyroid gland

The thyroid gland is attached to the trachea. The thyroid gland produces thyroxine which takes part in regulating functions such as the rate of chemical reactions in metabolism, heart rate and temperature control - its production is triggered by the hormone TSH produced in the pituitary gland (thyroid-stimulating hormone).

See also notes on thyroxine and

Homeostasis - thermoregulation, control of temperature

 

Adrenal gland

The adrenal gland are the top of the kidneys. The adrenal gland produces adrenaline which is used by the body to prepare for 'fight or flight' e.g. helps your body for action if you suffer trauma or find yourself in danger - its production is triggered by the ACTH hormone from the pituitary gland. (see notes on adrenaline)

 

The pancreas

The pancreas is situated below the stomach.  The pancreas produces insulin which regulates the glucose concentration ('level') in blood.

See Homeostasis - control of blood sugar level - insulin and diabetes

 

The ovaries (female only)

The ovaries produce the sex hormone oestrogen which is part of the chemistry of the menstrual cycle.

Oestrogen gives girls their female features such as breasts, soft skin, feminine voice and prepares the womb for a baby.

 

The testes (male only)

The testes produce testosterone, a hormone that controls puberty and sperm production in males.

Testosterone is a sex hormone that gives boys their male features such as deeper voices and more body hair than females.

 

Reminder: Homeostasis the function of self-regulating processes by which biological systems (organisms) tend to maintain physical and chemical stability while adjusting to conditions that are optimal for survival i.e. counteracting unfavourable conditions.

These process can involve hormones secreted from the glands of the endocrine system.

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Key points Based on the syllabus-specifications for students taking the AQA, Edexcel and OCR GCSE level biology examinations (~US grades 9-10).

Key points of an overview of the endocrine system and associated hormones

Endocrine System Overview

The endocrine system is a vital communication system in the body that uses hormones - chemical messengers - to regulate bodily functions over the long term.

• Hormones are secreted directly into the bloodstream by endocrine glands.

• Unlike the nervous system (which sends rapid electrical messages), the endocrine system is slower-acting but longer-lasting.

• Hormones control many processes such as growth, metabolism, blood sugar levels, water balance, reproduction, and the fight-or-flight response.

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Key Endocrine Glands and Their Hormones

Gland / Organ	Hormone(s) Secreted	Function(s)
Pituitary Gland (“master gland”)	- ADH (Antidiuretic hormone) - FSH (Follicle-stimulating hormone) - LH (Luteinising hormone) - TSH (Thyroid-stimulating hormone) - Growth hormone (GH)	- ADH: controls water balance via kidneys - FSH/LH: regulate ovary/testes functions - TSH: stimulates thyroid hormone release - GH: promotes growth and cell repair
Thyroid Gland	- Thyroxine	- Regulates metabolic rate, heart rate, and temperature
Adrenal Glands	- Adrenaline (epinephrine)	- Prepares body for 'fight or flight': increases heart rate, diverts blood to muscles, raises blood glucose
Pancreas (also part of digestive system)	- Insulin - Glucagon	- Insulin: lowers blood glucose by helping cells absorb sugar - Glucagon: raises blood glucose by converting glycogen to glucose in liver
Ovaries (females)	- Oestrogen - Progesterone	- Oestrogen: controls development of female secondary sexual characteristics and menstrual cycle - Progesterone: maintains uterus lining during menstrual cycle and pregnancy
Testes (males)	- Testosterone	- Controls development of male secondary sexual characteristics and sperm production

Why It Matters in Human Biology

Understanding the endocrine system is essential for grasping how the body maintains internal balance (homeostasis) and responds to changes. It's involved in:

• Growth and development (especially during puberty)

• Energy regulation through metabolism

• Stress response via adrenaline

• Reproduction and fertility

• Water and glucose balance

Disruptions to this system can lead to medical conditions like diabetes, thyroid disorders, or infertility—hence its importance in real-life applications of biology.

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Summary of learning objectives and key words or phrases

Know where various hormones are produced in body from glands or organs of endocrine system, including the pituitary gland, thyroid gland, adrenal gland, pancreas, ovaries and testes and their functions and effects.

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