Endocrinology Flashcards
(100 cards)
Which hormone stimulates growth of breast ducts and alveoli?
oestrogens
Which hormone stimulates proliferation of breast lobules?
Progesterones
Which hormone stimulates milk production?
Prolactin
Which hormone stimulates milk let down?
Oxytocin
Where in the adrenal gland is aldosterone produced?
Zona glomerulosa
What is a summary of the effects of aldosterone?
Works to increase retention of sodium and water and therefore to increase intravascular volume
Where does aldosterone act in the kidneys?
Distal convoluted tubule and collecting ducts
How does aldosterone act on the kidney?
It acts on nuclear mineralocorticoid receptors to increase the number of basolateral sodium/potassium channels. More sodium is pumped out of the cells in exchange for potassium in the extracellular fluid, and this sets up a concentration gradient which causes the movement of sodium out of the tubular lumen and into the tubule cells across the apical membrane. Thus, sodium is retained.
Where else does aldosterone act apart from the kidneys?
Sweat glands, colon
What does aldosterone do in the collecting ducts and in the colon?
increases the number of epithelial sodium channels (ENaCs) in the collecting ducts and the colon, increasing the permeability of the apical membrane to sodium. Other effects include secretion of potassium and protons (H+) into the tubular fluid, increasing loss of these two ions
What stimulates aldosterone production?
Aldosterone secretion is stimulated by hyperkalaemia, a rise in angiotensin II or ACTH, or decreased blood pressure (detected by atrial stretch receptors).
What conditions lead to a rise in aldosterone levels?
Increased secretion is seen in pregnancy, trauma, burns and blood loss.
What are the effects of cortisol?
Cortisol causes mobilisation of protein, lipid and carbohydrate stores, and immunosuppression.
What are the effects of too much cortisol?
Excess levels cause muscle wasting, a characteristic fat deposition around the abdomen and between the scapulae, thin skin and striae, psychiatric disorders, hyperglycaemia and diabetes mellitus, poor healing, osteoporosis, oedema, and fluid retention.
What is Cushing’s syndrome?
An excess of glucocorticoids.
2 types ACTH dependent (i.e. from a secreting tumour in the pituitary) and ACTH independent (i.e. taking too much steroid, adrenal carcinoma)
What suppresses ACTH production?
Excess glucocorticoid has a negative feedback and suppresses production
How many amino acids does the mature form of PTH include?
84
6 amino acids are removed from the PTH precursor in the golgi apparatus
What effect does oestrogen have on GnRH?
Estrogen stimulates GnRH secretion by a positive feedback effect on the hypothalamus.
What happens to basal body temperature during the follicular phase of the menstrual cycle?
It gradually declines and then rises at the time of ovulation due to the effects of progesterone
At what stage of pregnancy does the placenta make enough hormones to support foetal life and development?
The placenta makes enough progesterones and oestrogens to support foetal development from around the sixth week of pregnancy. Prior to this, the ovaries produce these sex hormones, and removal of the ovaries will result in termination of the pregnancy. After six or more weeks, the pregnancy will survive even if the ovaries are removed.
How does thyroxine circulate in the blood?
Thyroxine is bound in the greatest amount to thyroid-binding globulin and in smaller amounts to thyroid binding albumin and prealbumin.
How do thyroid hormones effect erythrocytes?
Thyroid hormones stimulate erythrocyte production by causing the maturation of erythrocyte progenitors.
What effect do thyroid hormones have on the oxygen dissociation curve?
They increase oxygen dissociation from haemoglobin
What are oestrogens?
Oestrogens are C18 steroids, and include estriol, estrone and 17-beta estradiol.