Ageing Endocrine System PDF

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Ageing Endocrine System

 Introduction to hormones  Overview of the endocrine system (ES)  Recap of some endocrine disorders  Endocrine changes (and some associated diseases) during ageing Outcomes: Know the most important endocrine diseases effecting the elderly Appreciate the importance of geriatric endocrinology Describe hormone changes occurring during aging Aging hormonal systems (“pauses”) Hormone secreting organs;         

Pineal gland Hypothalamus Pituitary gland Thyroid Parathyroid gland Thymus Adrenal gland Pancreas Ovaries/testes

Biological aging is characterized by the progressive deterioration of the function of all tissues and organs, leading to the loss of ability to restore homeostasis under stressful conditions and, consequently, to the increased risk of development of aging-related diseases. This also affects the neuroendocrine function of the hypothalamus-pituitary axis, influences the structure and function of the peripheral endocrine organs. Ageing also affects the number and sensitivity of receptors and may result in reduced responsiveness of target tissues to hormones and neurotransmitters. It is sometimes difficult to distinguish the effects of ageing on a endocrine physiology as effects caused by diseases can leave similar signs and symptoms. As well as being similar, signs and symptoms in the elderly can also be poorly expressed and atypical. The endocrine systems main purpose is to maintain a homeostatic environment through the use of hormones, hormones are essentially signalling chemicals. The endocrine system works in combination with the nervous system, so the neuroendocrine system tries to maintain a homeostatic environmental by sending out signals. The difference between both systems is that the nervous system is much faster so when a stimulus arrives at a neuron, the neuron will pass on this signal in the form of neurotransmitters that will then target a particular cell by binding onto its receptor that will cause the target cell to initiate a short-term quick response.

The endocrine system on the other hand, will send signals in the form of hormones (rather than neurotransmitters). When an endocrine cell is stimulated it will release hormones which will travel via the bloodstream where they will then target a cell and binds to its specific receptors. This will cause a target cell to initiate a long-term slow response. This type of signalling is called ‘endocrine signalling’. Hormones don’t always have to be secreted into the bloodstream to target cells. They can also secrete hormones that target cells nearby (therefore does not need to travel via bloodstream) this type of secretion is called paracrine signalling and this will initiate a long-term slow response. When the endocrine cell secretes hormones into the bloodstream, it can be in freeform and can be cleared quickly by the body. Or it can travel whilst bound to a protein, these hormones are usually lipid hormones, and as they are hydrophobic they cannot travel in liquid, these are called ‘protein-bound hormones’. Hormones can be grouped into 3 types;  Amino acid derivatives  Peptide hormones  Lipid derivatives e.g. steroid or thyroid hormones These hormones will bind onto the target cells specific receptor that will initiate a desired, long-term response. Peptide hormones, and most hormones that are derived from amino acids, they bind onto receptors on the plasma membrane. (receptors on the surface of the cell) Lipid derived hormones cross the cell membrane and bind to receptors in the cytoplasm (receptors within the cell). Example of endocrine response in a negative feedback loop Blood Glucose - Stimulus: Low blood glucose - This stimulates an endocrine cell in the pancreas called an alpha cell which will release glucagon into the blood stream. - The glucagon will then travel to a target cells in the liver, via the bloodstream and stimulate it to break down glycogen and secrete glucose into the blood which will increase blood glucose levels. - When blood glucose increases, a negative feedback signal will be sent back to stop stimulating the alpha cell and prevent further secretion of glucose. This is called a negative feedback loop Endocrine glands; Hypothalamus – Responsible for the production of anti-diuretic hormone (ADH) and oxytocin, plus the production of regularity hormones Pituitary gland – Located right below the hypothalamus, it has two lobes, posterior and anterior lobe. Posterior lobe – secretes oxytocin and ADH (produced by the hypothalamus).

Anterior lobe – secretes; adrenocorticotrophic hormone (ACTH), thyroid stimulating hormone (TSH), grown hormone (GH), prolactin (PRL) and follicle stimulating hormone (FSH), and luteinizing hormone (LH). ALL of these hormones are regulated by hormones produced by the hypothalamus. Pineal gland - Secretes melatonin. A women’s reproductive fitness is limited by her age. Discuss this with reference to ovarian reserve and menopause. Discuss endocrine diseases associated with aging. Describe and discuss endocrine and hormone changes associated with ageing.

Introduction What is endocrine system?...