1.1 Outline the structure and function of the endocrine system.  

1.2 Describe the function of five key hormones.  

1.3 Explain the principles of homeostasis in terms of receptors, effectors and negative feedback.  

1.4 Explain how homeostasis is maintained using negative feedback mechanisms.  

2. Understand the effects of hormones.  

2.1 Evaluate the effects of the imbalance of hormones.   

2.2 Discuss the effect of the natural decline in hormones in the Menopause and the value of HRT.  

Pituitary gland

Pineal

Thyroid gland and parathyroid glands

Thymus

Adrenal glands

Pancreas (Islets of Langerhans)

Testes

Ovaries

Very good blood supply to these glands.

Exocrine - Product secreted from the gland/duct (sweat / saliva / breastmilk / tears)

Primary ovarian insufficiency (POI), also known as premature ovarian failure, occurs when a woman's ovaries stop functioning normally before she turns 40. It's caused by early egg loss or follicular dysfunction. POI differs from early or premature menopause. Short-term effects may include hot flushes, night sweats, headaches, or heart palpitations. Long-term risks include infertility, osteoporosis, cardiovascular and neurological diseases, and a higher risk of early death. 

Oestrogen and testosterone - main hormones involved in the development of the female and male reproductive characteristics.

Oestrogen is often called the female sex hormone

Testosterone is often called the male sex hormone.

However, both hormones are found in males and females.

Females have much higher levels of oestrogen, while males have much higher levels of testosterone.

Puberty is initiated by secretion of gonadotropin-releasing hormone (GnRH) from the hypothalamus.

GnRH acts on the anterior pituitary and stimulates the secretion of FSH and LH.

GnRH in both females and males - responsible for stimulating ovaries and testes to begin secreting the sex hormones.

Leads to development a) female and male reproductive organs, b) secondary sex characteristics such as pubic and underarm (axillary) hair in both sexes, facial hair and increased muscle mass in males, and widening of the hips and breast development in females.

Females are born with hundreds of thousands of ova (egg cells) in their ovaries.

Secretion of FSH and LH by the anterior pituitary leads to the onset of the menstrual cycle.

In males, LH stimulates secretion of testosterone by the testes.

FSH makes cells in the testes more receptive to testosterone which leads to sperm production.

Menopause can also occur when the ovaries are damaged by specific treatment such as chemotherapy or radiotherapy, or when the ovaries are removed, often at the time of a hysterectomy.

Ovaries naturally fail to produce estrogen and progesterone when they have few remaining egg cells; the maximum number of egg cells in the ovaries is present before birth, with a reduced number already at birth, gradual reduction from puberty, and a rapid decline from 40 onwards.

With less egg cells, the ovaries become less able to respond to hormones from the pituitary gland in the brain: follicle stimulating hormone (FSH) and luteinising hormone (LH) and less oestrogen is produced.

Levels of FSH and LH subsequently rise and a measurement of FSH is sometimes used to diagnose menopause. The resulting low, and changing levels of ovarian hormones, particularly estrogen, are thought to be the cause of menopausal symptoms and later consequences in many women.

The term climacteric refers to the time in which the hormone levels are changing, up to the periods stopping; reducing and changing hormone levels can cause early menopausal symptoms.

At this stage, there may still be enough hormones produced to stimulate the lining of the womb (endometrium) to produce monthly periods (menstruation).

Perimenopause is the stage from the beginning of menopausal symptoms to the postmenopause.

Menopause means the last menstrual period. Periods stop because the low levels of estrogen and progesterone do not stimulate the lining of the womb (endometrium) in the normal cycle.

Hormone levels can fluctuate for several years before eventually becoming so low that the endometrium stays thin and does not bleed.

Postmenopause is the time following the last period, and is usually defined as more than 12 months with no periods in someone with intact ovaries, or immediately following surgery if the ovaries have been removed.

The average age of the natural menopause is 51 years, but can occur much earlier or later. Menopause occurring before the age of 45 is called early menopause and before the age of 40 is premature menopause.

• Menopause usually affects those aged 45 to 55, but can happen earlier. The average age is 51, says The Menopause Charity.

• Around 3% to 8% of those experiencing menopause are aged between 40 and 44, according to the National Institute for Health and Care Excellence (NICE).

• 1% have premature ovarian insufficiency with perimenopause starting before 40 years old. It may be triggered by surgery, cancer treatment, an underlying condition, or an autoimmune disease.

• Menopause symptoms have a median duration of 7 years, according to NICE. 

• According to a report by the Fawcett Society, 1 in 10 women have left work because of menopause symptoms, while 77% describe one or more menopausal symptoms as ‘very difficult’. 

Very good blood supply to these glands.

Exocrine - Product secreted from the gland/duct (sweat / saliva / breastmilk / tears)