There are a number of biological rhythms controlled by a pacemaker near the hypothalamus. Releasing hormones are discharged episodically in pulses from the hypothalamus rather than as a continuous flow. External stimuli including darkness and light (circadian rhythm) and the sleep-wake cycles influence the releasing hormone pulse Frequency. Abnormality of these biorhythms may be responsible for some types of abnormal reproductive function.
There are usually negative feed back systems that reduce stimulating hormone release. As oestrogen levels rise, the gonadotrophin, the hormones that influence the production of the sex steroids ovaries, output falls (Figure 2.6). the whole setup is known as the hypothalamic-pituitary ovarian axis.
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Figure 2.6 Hypothalamic-pituitary ovarian axis
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- 1 What is meant by the term anatomy?
- 2 What is the anatomy of the external genital area?
- 3 What are the internal genital organs?
- 4 What is the peritoneum?
- 5 Why did I develop into a girl?
- 6 How do sperm development and egg development differ?
- 7 What is meant by the term physiology?
- 8 What is a hormone?
- 9 What are steroid hormones?
- 10 What is sex hormone binding globulin?
- 11 What controls sex hormone release?
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This is the personal website of David A Viniker MD FRCOG, Consultant Obstetrician and Gynaecologist at Whipps Cross University Hospital, London - Specialist Interests - Reproductive Medicine including Infertility, PCOS, PMS, Menopause and HRT.
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