📚 Hormones: Sources, Roles and Effects | 激素：来源、作用与效应
Hormones are chemical messengers produced by endocrine glands. They travel in the bloodstream to target organs, where they trigger specific responses that help regulate many body functions, from growth to metabolism and reproduction. Understanding where each hormone comes from and what it does is essential for explaining how the body maintains a stable internal environment and reacts to changes.
激素是由内分泌腺产生的化学信使。它们通过血液循环到达靶器官，引发特定的反应，从而帮助调节许多身体功能，包括生长、代谢和生殖。理解每种激素的来源及其作用对于解释人体如何维持稳定的内环境以及如何应对变化至关重要。
1. Introduction to Hormonal Control | 激素调控简介
Hormones are secreted directly into the blood, unlike enzymes which act at their site of production. Because they circulate throughout the body, a single hormone can affect several different organs, yet only cells with the correct receptor proteins will respond. This specificity ensures that hormonal signals are precise even though they are distributed widely.
激素直接分泌到血液中，这与在产生部位起作用的酶不同。由于激素随血液循环全身，一种激素可以影响多个不同的器官，但只有拥有正确受体蛋白的细胞才会作出反应。这种特异性确保了激素信号虽然分布广泛，但作用精确。
The endocrine system works more slowly than the nervous system but produces longer-lasting effects. Key endocrine glands in the human body include the pituitary gland, thyroid, adrenal glands, pancreas, ovaries and testes. IGCSE candidates are expected to know the sources, roles and effects of six major hormones: ADH, adrenaline, insulin, testosterone, oestrogen and progesterone.
内分泌系统比神经系统作用慢，但产生的效果更持久。人体内主要的内分泌腺包括垂体、甲状腺、肾上腺、胰腺、卵巢和睾丸。IGCSE考生需要掌握六种重要激素的来源、作用和效应：抗利尿激素(ADH)、肾上腺素、胰岛素、睾酮、雌激素和孕酮。
2. Sources of the Six Key Hormones | 六种关键激素的来源
The table below summarises where each of the six hormones is produced and, where relevant, stored. A clear understanding of these glands helps you link hormonal action to specific organs.
下表总结了这六种激素的产生部位以及（如适用）储存部位。清楚地了解这些腺体有助于你将激素作用与特定器官联系起来。
| Hormone | Source |
|---|---|
| ADH (antidiuretic hormone) | Produced by the hypothalamus, stored and released by the posterior pituitary gland 由下丘脑产生，储存于垂体后叶并释放 |
| Adrenaline | Adrenal glands (medulla region) 肾上腺（髓质） |
| Insulin | Pancreas (β-cells in the islets of Langerhans) 胰腺（胰岛β细胞） |
| Testosterone | Testes (Leydig cells) 睾丸（间质细胞） |
| Oestrogen | Ovaries (developing follicles) 卵巢（发育中的卵泡） |
| Progesterone | Corpus luteum in the ovary, and the placenta during pregnancy 卵巢黄体，以及怀孕时的胎盘 |
Note that ADH is unusual because its synthesis and release are separated between the hypothalamus and posterior pituitary. All the other hormones in this list are both made and released by the same gland.
请注意，ADH比较特殊，因为它的合成和释放分别在下丘脑和垂体后叶完成。列表中其他激素均由同一腺体产生并释放。
3. ADH and Water Balance | 抗利尿激素与水分平衡
ADH's main role is to control the water content of the blood. It acts on the collecting ducts in the kidneys, making their walls more permeable to water. As a result, more water is reabsorbed from the filtrate back into the blood, producing a smaller volume of concentrated urine.
ADH的主要作用是控制血液中的含水量。它作用于肾脏的集合管，使其管壁对水的通透性增加。结果，更多的水从滤液中被重新吸收回血液，从而产生量少且浓缩的尿液。
When the blood becomes too concentrated (e.g. after sweating or drinking too little water), osmoreceptors in the hypothalamus detect the increase in solute concentration. The hypothalamus then sends signals to the posterior pituitary to release more ADH. This negative feedback loop ensures that blood water concentration returns to normal.
当血液变得过于浓缩时（例如出汗后或饮水过少），下丘脑中的渗透压感受器会探测到溶质浓度的升高。然后下丘脑发送信号至垂体后叶，使其释放更多的ADH。这种负反馈回路确保血液中的水浓度恢复到正常水平。
If blood is too dilute, ADH release is reduced, the collecting ducts become less permeable, less water is reabsorbed and a large volume of dilute urine is produced. This explains why drinking a lot of water results in frequent, pale urine.
如果血液过于稀释，ADH的释放减少，集合管的通透性降低，重吸收的水分减少，就会产生大量稀释的尿液。这就解释了为什么大量饮水后会出现尿频且尿液颜色浅的现象。
4. Adrenaline – The 'Fight or Flight' Hormone | 肾上腺素——“战或逃”激素
Adrenaline is released from the adrenal glands in response to stress, fear or excitement. Its role is to prepare the body for vigorous physical activity. It achieves this by increasing heart rate, raising blood pressure and boosting the supply of oxygen and glucose to the muscles and brain.
肾上腺素在身体遇到压力、恐惧或兴奋时由肾上腺释放。它的作用是为身体进行剧烈体力活动做好准备。通过增加心率、升高血压以及增加肌肉和大脑的氧气和葡萄糖供应来实现这一目的。
Adrenaline triggers the liver to convert stored glycogen into glucose and release it into the blood. This provides a rapid source of energy. At the same time, it diverts blood away from non-essential organs like the digestive system and towards skeletal muscles. Pupils dilate to improve vision, and mental alertness increases.
肾上腺素促使肝脏将储存的糖原转化为葡萄糖并释放到血液中，提供快速的能量来源。同时，它把血液从消化系统等非必需器官分流至骨骼肌。瞳孔放大以改善视力，精神警觉性也相应提高。
The effects of adrenaline are short-lived because the hormone is quickly broken down by enzymes in the liver. This temporary boost was vital for our ancestors when facing immediate danger; today it is still the reason for a 'rush' of energy in stressful moments.
肾上腺素的效果是短暂的，因为这种激素很快就会被肝脏中的酶分解。这种暂时的能量激增对我们祖先在面临即刻危险时至关重要；今天，它仍然是在紧张时刻感到“一阵能量冲激”的原因。
5. Insulin and Blood Glucose Regulation | 胰岛素与血糖调节
Insulin is released by the pancreas when blood glucose concentration rises above normal, for example after eating a carbohydrate-rich meal. Its role is to lower blood glucose back to the normal range. Insulin stimulates the liver and muscle cells to absorb glucose and convert it into glycogen for storage. This process is called glycogenesis.
当血糖浓度升高到正常值以上时（例如吃了富含碳水化合物的食物后），胰腺会释放胰岛素。它的作用是将血糖降低到正常范围。胰岛素刺激肝脏和肌肉细胞吸收葡萄糖，并将其转化为糖原储存起来。这个过程称为糖原生成。
Insulin also promotes the uptake of glucose by many other body cells, increasing their rate of respiration. Without sufficient insulin, or if cells become resistant to its signal, blood glucose remains dangerously high, a condition known as diabetes mellitus.
胰岛素还促进许多其他体细胞摄取葡萄糖，提高它们的呼吸速率。如果没有足够的胰岛素，或者细胞对胰岛素信号产生抵抗，血糖就会持续保持在危险的高水平，这种状态称为糖尿病。
When blood glucose falls too low, the pancreas releases a different hormone, glucagon, which stimulates the liver to break down glycogen back into glucose. Although insulin is the focus in this specification, recognising its role in this homeostatic pair is helpful for understanding negative feedback.
当血糖过低时，胰腺释放另一种激素——胰高血糖素，它刺激肝脏将糖原分解回葡萄糖。虽然胰岛素是教学大纲的重点，但认识到它在这一稳态配对中的作用有助于理解负反馈。
6. Testosterone – The Main Male Sex Hormone | 睾酮——主要的雄性激素
Testosterone is produced by the testes and is responsible for the development of male secondary sexual characteristics. During puberty, rising levels of testosterone cause the voice to deepen, the growth of facial and body hair, increased muscle mass and the enlargement of the penis and testes.
睾酮由睾丸产生，负责男性第二性征的发育。在青春期，睾酮水平的升高导致声音变低沉、面部和体毛生长、肌肉量增加以及阴茎和睾丸增大。
In addition to physical changes, testosterone stimulates spermatogenesis – the production of sperm in the seminiferous tubules of the testes. This is a continuous process from puberty onwards, allowing males to produce gametes throughout adult life.
除了身体变化外，睾酮还刺激精子发生——即在睾丸生精小管中产生精子。从青春期开始这是一个持续的过程，使男性在整个成年期都能产生配子。
Testosterone also influences behaviour, contributing to increased libido and competitiveness. Its levels are regulated by hormones from the pituitary gland (LH and FSH), maintaining the optimal concentration for reproduction and development.
睾酮还影响行为，导致性欲和竞争力增强。它的水平受到垂体激素（LH和FSH）的调节，从而维持适合生殖和发育的最佳浓度。
7. Oestrogen – A Key Female Reproductive Hormone | 雌激素——一种重要的女性生殖激素
Oestrogen is mainly secreted by the ovaries as the ovarian follicles develop during the menstrual cycle. It plays a central role in regulating the menstrual cycle and preparing the body for a potential pregnancy. Oestrogen stimulates the repair and thickening of the uterus lining (endometrium) after menstruation.
雌激素主要在月经周期中随着卵巢卵泡的发育由卵巢分泌。它在调节月经周期和为身体可能怀孕做准备方面起着核心作用。雌激素刺激月经后子宫内膜的修复和增厚。
At puberty, oestrogen promotes the development of female secondary sexual characteristics: breast development, widening of the hips and the start of menstrual cycles. It also affects the distribution of body fat, giving the female body its typical shape.
在青春期，雌激素促进女性第二性征的发育：乳房发育、髋部变宽以及月经周期的开始。它还影响体脂分布，塑造了典型的女性体型。
Oestrogen also exerts positive feedback on LH secretion just before ovulation, causing a surge in LH that triggers the release of a mature egg. Later in the cycle, oestrogen levels drop if fertilisation does not occur, leading to the breakdown of the uterine lining.
雌激素还在排卵前对LH的分泌产生正反馈作用，导致LH激增，从而触发成熟卵子的释放。在周期后期，如果没有受精，雌激素水平下降，导致子宫内膜脱落。
8. Progesterone – Maintaining the Uterus Lining | 孕酮——维持子宫内膜
Progesterone is produced predominantly by the corpus luteum, which forms from the empty follicle after ovulation. Its main role is to maintain the thick, blood-rich lining of the uterus so that a fertilised egg can implant and develop. Progesterone keeps the endometrium stable and prevents contractions of the uterine muscles.
孕酮主要由排卵后空卵泡形成的黄体产生。它的主要作用是维持厚实且血液供应丰富的子宫内膜，以便受精卵能够着床和发育。孕酮保持子宫内膜稳定，并防止子宫肌肉收缩。
During pregnancy, the placenta takes over progesterone production, maintaining high levels that prevent further ovulation and menstruation. If fertilisation does not occur, the corpus luteum breaks down, progesterone levels fall sharply, and this drop triggers the shedding of the uterine lining – menstruation.
在怀孕期间，胎盘接替产生孕酮，维持较高的激素水平，从而阻止进一步的排卵和月经。如果没有受精，黄体退化，孕酮水平急剧下降，这种下降引发了子宫内膜的脱落——月经。
Progesterone also works alongside oestrogen to prepare the breasts for milk production, although prolactin takes over lactation after birth. The interplay between oestrogen and progesterone throughout the menstrual cycle is vital for female fertility.
孕酮还与雌激素协同作用，为乳房泌乳做准备，尽管分娩后催乳素主导泌乳。整个月经周期中雌激素和孕酮的相互作用对女性生育能力至关重要。
9. Comparing the Roles of the Six Hormones | 六种激素作用的比较
The six hormones can be grouped by the processes they control: homeostasis (ADH and insulin), immediate stress response (adrenaline) and reproduction (testosterone, oestrogen and progesterone). It is useful to compare their modes of action and target organs to see how hormones coordinate complex body functions.
这六种激素可以根据其控制的过程进行分类：稳态（ADH和胰岛素）、即时应激反应（肾上腺素）和生殖（睾酮、雌激素和孕酮）。比较它们的作用方式和靶器官有助于理解激素如何协调复杂的身体功能。
| Hormone | Main Target(s) | Primary Effect |
|---|---|---|
| ADH | Kidneys (collecting ducts) | Water reabsorption, urine concentration |
| Adrenaline | Heart, liver, muscles, eyes | Increased heart rate, glycogen breakdown, diverted blood flow, dilated pupils |
| Insulin | Liver, muscles, body cells | Glucose uptake and storage as glycogen |
| Testosterone | Testes, muscles, bones, hair follicles | Sperm production, male secondary sexual characteristics |
| Oestrogen | Uterus, breasts, pituitary gland | Repair of uterus lining, female secondary sexual characteristics |
| Progesterone | Uterus, mammary glands | Maintenance of uterus lining, inhibition of contractions |
Notice that some hormones act primarily on a single organ (e.g. ADH on kidneys), whereas others, like adrenaline, affect multiple organ systems simultaneously to create a coordinated whole-body response. All of these hormones are regulated by feedback mechanisms.
请注意，有些激素主要作用于单一器官（如ADH作用于肾脏），而另一些激素，如肾上腺素，则同时影响多个器官系统，产生协调的全身反应。所有这些激素都受到反馈机制的调节。
10. Negative Feedback and Homeostasis | 负反馈与稳态
regulation: high glucose → insulin released → glucose falls → insulin secretion decreases.
大多数激素控制系统依赖负反馈来维持内环境的恒定。当检测到变化时，会触发纠正性反应，一旦恢复到最适状态，激素的释放就会减少。这在血糖调节中非常明显：血糖高→释放胰岛素→血糖下降→胰岛素分泌减少。
In water balance, increased blood concentration stimulates ADH release, which causes water reabsorption. As blood concentration falls, the stimulus for ADH release disappears. In reproduction, the interplay of oestrogen and progesterone is also regulated by pituitary hormones via feedback loops, ensuring the menstrual cycle runs at a regular rhythm.
在水分平衡中，血液浓度升高会刺激ADH释放，导致水分重吸收。当血液浓度下降时，ADH释放的刺激消失。在生殖系统中，雌激素和孕酮的相互作用也通过反馈回路受到垂体激素的调节，确保月经周期的规律进行。
Positive feedback is rarer but does occur, for example when rising oestrogen initially stimulates even more LH release to trigger ovulation. Examiners often ask candidates to distinguish between negative and positive feedback using these examples.
正反馈较为罕见，但确实存在，例如雌激素水平的升高最初会刺激更多的LH释放，从而触发排卵。考官经常要求考生用这些例子来区分负反馈和正反馈。
11. Summary Table of Sources, Roles and Effects | 来源、作用及效应总结表
The table below provides a quick-reference revision summary combining the source, role and main effect of each hormone as required by the Edexcel IGCSE Biology specification.
下表提供了一个快速参考的复习总结，结合了Edexcel IGCSE生物学考试大纲中要求的每种激素的来源、作用和主要效应。
| Hormone | Source | Role | Effect |
|---|---|---|---|
| ADH | Hypothalamus / posterior pituitary | Regulates blood water content | Increases water reabsorption in kidneys; urine becomes concentrated |
| Adrenaline | Adrenal medulla | Prepares body for 'fight or flight' | Heart rate up; glycogen converted to glucose; pupils dilate; blood flow diverted to muscles |
| Insulin | Pancreas (β-cells) | Lowers blood glucose | Stimulates glucose uptake by cells; promotes glycogen storage in liver and muscles |
| Testosterone | Testes | Male sexual development and reproduction | Sperm production; deeper voice; facial hair; increased muscle mass |
| Oestrogen | Ovaries (follicles) | Regulates menstrual cycle; female sexual characteristics | Thickening of uterus lining; breast development; hip widening; triggers LH surge |
| Progesterone | Corpus luteum / placenta | Maintains uterus lining for pregnancy | Stabilises endometrium; inhibits uterine contractions; prevents menstruation during pregnancy |
By learning these patterns, you will be able to answer both straightforward recall questions and application-style questions that ask you to predict what would happen if a hormone level became too high or too low.
通过学习这些模式，你将能够回答直接的识记问题，也能应对要求预测某种激素水平过高或过低时会发生什么的应用型问题。
12. Exam Tips for Hormone Questions | 激素考题的考试技巧
When answering exam questions, always be precise about the source. For ADH, stating 'pituitary gland' alone may not gain full marks – specify 'posterior pituitary' and mention the hypothalamus if possible. Similarly, note that insulin is made by beta cells, and testosterone by the testes, not the pituitary.
在回答考题时，始终要精确说明来源。对于ADH，只说“垂体”可能得不到满分——应明确指出“垂体后叶”，并尽可能提到下丘脑。同样，注意胰岛素是由β细胞产生的，睾酮是由睾丸而非垂体产生的。
Use scientific terms such as 'glycogenesis', 'gluconeogenesis', 'glycogenolysis' and 'negative feedback' where appropriate, but only if you are confident in their meaning. Marks are often lost when candidates confuse the direction of glycogen conversion for insulin versus adrenaline.
在适当的时候使用科学术语，如“糖原生成”、“糖异生”、“糖原分解”和“负反馈”，但前提是你要确信它们的含义。考生经常因为混淆了胰岛素与肾上腺素促使糖原转化的方向而失分。
For graph-based questions showing hormone levels during the menstrual cycle, practice identifying the peak of LH, the rise in oestrogen before ovulation, and the elevated progesterone during the luteal phase. Linking these changes to events in the ovary and uterus is a common high-mark question.
对于显示月经周期中激素水平变化的图表题，要练习识别LH峰值、排卵前雌激素的升高以及黄体期孕酮的升高。将这些变化与卵巢和子宫中的事件联系起来是一道常见的高分值题目。
Always connect the effect of a hormone back to its role in maintaining homeostasis or enabling successful reproduction. For example, don't just state 'insulin lowers blood glucose' – explain that this prevents hyperglycaemia, bringing blood glucose back to the normal set point.
始终将激素的效应与其维持稳态或保障成功繁殖的作用联系起来。例如，不要只说“胰岛素降低血糖”，而要解释这可以防止高血糖，使血糖恢复到正常的设定值。
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