📚 3.12 Hormonal Control of the Menstrual Cycle | 3.12 月经周期的激素调节
The menstrual cycle is a monthly series of changes in the female reproductive system designed to prepare the body for pregnancy. It is controlled by four key hormones: FSH, LH, oestrogen and progesterone. In this article, we break down each hormone's role, the feedback mechanisms involved, and how to interpret typical exam graphs.
月经周期是女性生殖系统每月发生的一系列变化，旨在为怀孕做好准备。该过程由四种关键激素控制：卵泡刺激素（FSH）、黄体生成素（LH）、雌激素和孕酮。本文将逐一解析每种激素的作用、涉及的反馈机制，以及如何解读典型考试曲线图。
1. Overview of the Menstrual Cycle | 1. 月经周期概述
The menstrual cycle lasts on average 28 days, counted from the first day of one period to the first day of the next. It involves two main structures: the ovaries, which release eggs, and the uterus, whose lining changes to accept or shed a fertilised egg.
月经周期平均持续28天，从一次月经的第1天算起，到下一次月经的第1天结束。此过程涉及两个主要器官：负责释放卵子的卵巢，以及子宫内膜——其变化决定是否接纳或排出受精卵。
The cycle can be divided into the follicular phase, ovulation, the luteal phase and menstruation. Hormones coordinate these phases through tightly regulated feedback loops.
该周期可分为卵泡期、排卵期、黄体期和月经期。激素通过精密调控的反馈环路来协调这些阶段。
2. Key Hormones and Their Sources | 2. 关键激素及其来源
FSH (follicle-stimulating hormone) – released by the pituitary gland.
卵泡刺激素（FSH） – 由垂体释放。
LH (luteinising hormone) – released by the pituitary gland.
黄体生成素（LH） – 由垂体释放。
Oestrogen – produced by developing follicles in the ovaries.
雌激素 – 由卵巢中正在发育的卵泡产生。
Progesterone – produced by the corpus luteum (a temporary endocrine structure after ovulation).
孕酮 – 由黄体（排卵后形成的临时内分泌结构）产生。
The table below summarises the source and main function of each hormone.
下表总结了每种激素的来源和主要功能。
| Hormone 激素 | Source 来源 | Main function 主要功能 |
| FSH | Pituitary gland 垂体 | Stimulates follicle growth and oestrogen production 刺激卵泡生长和雌激素产生 |
| Oestrogen 雌激素 | Ovaries (follicles) 卵巢（卵泡） | Thickens uterus lining; triggers LH surge 增厚子宫内膜；触发LH峰值 |
| LH | Pituitary gland 垂体 | Triggers ovulation; forms corpus luteum 触发排卵；形成黄体 |
| Progesterone 孕酮 | Corpus luteum 黄体 | Maintains uterus lining; inhibits FSH/LH 维持子宫内膜；抑制FSH/LH |
3. The Role of FSH | 3. FSH的作用
At the start of the cycle, the pituitary gland releases FSH. FSH travels through the blood to the ovaries, where it stimulates one or more follicles to develop. Each follicle contains an immature egg.
在周期开始时，垂体释放FSH。FSH通过血液到达卵巢，刺激一个或多个卵泡发育。每个卵泡内包含一个未成熟的卵子。
FSH also stimulates the follicle cells to produce oestrogen. Early in the cycle, as FSH levels rise, the oestrogen level gradually increases.
FSH还刺激卵泡细胞产生雌激素。周期早期，随着FSH水平升高，雌激素水平逐渐上升。
FSH → Follicle growth → Oestrogen secretion
FSH → 卵泡生长 → 雌激素分泌
4. The Role of Oestrogen | 4. 雌激素的作用
Oestrogen has several important effects. It causes the lining of the uterus (endometrium) to thicken and develop more blood vessels, preparing a suitable environment for a potential embryo.
雌激素具有多个重要作用。它使子宫内膜增厚并发育出更多血管，为可能的胚胎准备适宜环境。
Oestrogen also affects the pituitary gland. At moderate levels, it inhibits FSH production, preventing too many follicles from developing. However, when oestrogen levels become very high (around day 12–13), it stimulates the pituitary to release a large burst of LH – this is called the LH surge.
雌激素还会影响垂体。在中等水平时，它抑制FSH的产生，防止过多卵泡发育。然而，当雌激素水平变得非常高时（约第12–13天），它会刺激垂体释放大量LH——这称为LH高峰。
This positive feedback loop ensures that only one dominant follicle matures fully and that ovulation happens at the correct time.
这种正反馈环路确保只有一个优势卵泡完全成熟，并确保排卵在正确时间发生。
5. The Role of LH | 5. 黄体生成素的作用
LH is released from the pituitary gland. In response to the high oestrogen level, LH rises sharply and triggers ovulation, the release of a mature egg from the follicle on about day 14.
LH由垂体释放。在高水平雌激素的刺激下，LH急剧升高并触发排卵，即大约在第14天从卵泡中释放成熟卵子。
After ovulation, LH stimulates the empty follicle to develop into the corpus luteum. The corpus luteum then secretes progesterone.
排卵后，LH刺激空卵泡发育成黄体。黄体随后分泌孕酮。
LH surge → Ovulation → Corpus luteum formation → Progesterone
LH高峰 → 排卵 → 黄体形成 → 孕酮
6. The Role of Progesterone | 6. 孕酮的作用
Progesterone is often called the 'pregnancy-protecting hormone'. It maintains the thickened uterine lining and prevents it from breaking down. It also inhibits the release of FSH and LH from the pituitary, preventing another ovulation during the same cycle.
孕酮常被称为“保护妊娠激素”。它维持增厚的子宫内膜，防止其脱落。同时，它抑制垂体释放FSH和LH，阻止同一周期内再次排卵。
If fertilisation does not occur, the corpus luteum degenerates after about 14 days. Progesterone levels then fall, the uterine lining breaks down, and menstruation begins.
如果未发生受精，黄体大约在14天后退化。随后孕酮水平下降，子宫内膜脱落，月经开始。
If fertilisation does occur, the developing embryo produces human chorionic gonadotropin (hCG), which maintains the corpus luteum so that progesterone levels remain high.
如果发生受精，发育中的胚胎会分泌人绒毛膜促性腺激素（hCG），维持黄体，使孕酮水平保持高水平。
7. The Feedback Mechanisms | 7. 反馈机制
Hormonal control relies on positive and negative feedback. In the follicular phase, rising oestrogen has a negative feedback effect on FSH, keeping FSH low so that only one follicle survives.
激素调节依赖于正反馈和负反馈。在卵泡期，不断上升的雌激素对FSH产生负反馈效应，使FSH维持较低水平，从而只有一个卵泡存活。
Near day 12–13, oestrogen switches to positive feedback on the pituitary, causing a huge release of LH. This is an example of positive feedback leading to a rapid event (ovulation).
第12–13天前后，雌激素变为对垂体的正反馈，导致大量LH释放。这是正反馈导致快速事件（排卵）的一个例子。
After ovulation, progesterone and oestrogen from the corpus luteum exert negative feedback on the pituitary, keeping FSH and LH suppressed. If pregnancy does not occur, the fall in progesterone removes this inhibition, allowing the next cycle to begin.
排卵后，黄体分泌的孕酮和雌激素对垂体产生负反馈，抑制FSH和LH的释放。如果未怀孕，孕酮下降解除这种抑制，使下一周期开始。
8. The Menstrual Cycle Timeline | 8. 月经周期时间线
Day 1–5: Menstruation – Uterine lining breaks down; FSH begins to rise.
第1–5天：月经期 – 子宫内膜脱落；FSH开始升高。
Day 1–13: Follicular phase – Follicle matures; oestrogen rises; LH remains low.
第1–13天：卵泡期 – 卵泡成熟；雌激素升高；LH保持较低。
Day 14: Ovulation – LH surge triggers egg release.
第14天：排卵期 – LH高峰触发卵子释放。
Day 15–28: Luteal phase – Corpus luteum forms; progesterone high; uterine lining maintained.
第15–28天：黄体期 – 黄体形成；孕酮升高；子宫内膜维持。
This timeline is the basis for understanding graph questions in the exam.
这个时间线是理解考试中曲线图问题的基础。
9. Common Exam Focus: Interpreting Graphs | 9. 考试重点：解读曲线图
You may be asked to label a graph showing hormone levels over a 28-day cycle. Remember the characteristic patterns:
你可能会被要求标注一个28天周期内激素水平的曲线图。记住这些典型模式：
FSH is highest at the very beginning, then falls and stays low.
FSH在周期开始时最高，随后下降并保持低位。
Oestrogen peaks just before ovulation (around day 12–13).
雌激素在排卵前（约第12–13天）达到峰值。
LH shows a sharp single peak at day 14.
LH在第14天出现一个尖锐的单一高峰。
Progesterone is low in the first half, rises after ovulation, and falls near day 28 if no pregnancy.
孕酮在前半段较低，排卵后升高，若未怀孕则在第28天前下降。
FSH: early peak → low | Oestrogen: pre-ovulation peak → moderate | LH: sharp day-14 peak | Progesterone: post-ovulation rise → fall
FSH：早期高峰 → 低 | 雌激素：排卵前高峰 → 中等 | 孕酮：排卵后升高 → 下降
10. Clinical Applications and Contraception | 10. 临床应用与避孕
Understanding these hormones explains how some contraceptive pills work. Most birth control pills contain oestrogen and/or progesterone. These hormones inhibit FSH and LH production, so no follicle matures and no ovulation occurs.
理解这些激素可解释某些避孕药的作用原理。大多数避孕药含有雌激素和/或孕酮。这些激素抑制FSH和LH的产生，因此没有卵泡成熟，也就不会排卵。
Fertility treatments may use FSH and LH injections to stimulate multiple follicles and induce ovulation in women who have low natural hormone levels.
生育治疗可使用FSH和LH注射剂来刺激多个卵泡发育，并诱导激素水平低下的女性排卵。
Exam questions often link hormonal control to these real-world applications.
考试题通常将激素调节与这些实际应用联系起来。
11. Summary Table | 11. 总结表
| Stage 阶段 | Dominant hormone 主要激素 | Effect 效应 |
| Early follicular 卵泡早期 | FSH ↑ | Follicle growth 卵泡生长 |
| Late follicular 卵泡晚期 | Oestrogen ↑↑ | Uterus lining thickens; LH surge 子宫内膜增厚；LH高峰 |
| Ovulation 排卵期 | LH peak | Egg released 卵子释放 |
| Luteal 黄体期 | Progesterone ↑ | Maintains lining; inhibits FSH/LH 维持内膜；抑制FSH/LH |
| Late luteal / menstruation 黄体晚期/月经期 | Progesterone ↓ | Lining breaks down 内膜脱落 |
12. Exam Tips | 12. 考试技巧
using FSH with LH. Remember: FSH = Follicle Stimulating Hormone; LH = Luteinising Hormone.
始终使用全称，避免混淆FSH和LH。记住：FSH = Follicle Stimulating Hormone（卵泡刺激素）；LH = Luteinising Hormone（黄体生成素）。
Link each hormone to its effect: FSH grows follicles, oestrogen builds the lining and triggers LH, LH causes ovulation, progesterone maintains the lining.
将每种激素与其效应联系起来：FSH促进卵泡生长，雌激素增厚内膜并触发LH，LH导致排卵，孕酮维持内膜。
For graph questions, label the LH surge and the progesterone fall. These are the most commonly tested features.
对于曲线图题，标出LH高峰和孕酮下降。这两个是最常考的特征。
Be precise about negative feedback: high oestrogen in the early cycle inhibits FSH; high progesterone later inhibits both FSH and LH.
关于负反馈要表述精确：周期早期的雌激素抑制FSH；后期的高孕酮抑制FSH和LH。
Mastering these hormonal interactions will help you answer both multiple-choice and extended-response questions with confidence.
掌握这些激素相互作用，将帮助你自信地回答选择题和拓展回答题。
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