L11- Introduction to the hypothalamic-pituitary axis Flashcards
Where is growth hormone synthesised?
By the somatotrophe cells of the anterior pituitary gland.
What are the 2 hormones that control the release of growth hormone and where are they released from?
Growth hormone releasing hormone (somatotropin) stimulates the release of GH. Growth hormone inhibiting hormone (somatostatin) prevents the release of GH. They are secreted from the hypothalamus.
What does oxytocin do?
Oxytocin acts via IP3 (calcium influx) to cause contraction of the smooth muscle of the genital tract (uterus) and the breast.
Where is prolactin secreted from?
The lactotroph cells in the anterior pituitary gland.
What hormones control the release of prolactin?
Prolactin release inhibiting factor (dopamine) which prevents the release. TRH stimulates the release. They are both released from the hypothalamus. Secretion is stimulated by: mild stress, nipple stimulation and coitus (sex).
Why does ovulation not occur during breastfeeding?
Prolactin levels increase as this controls the milk production. Prolactin inhibits gonadotrophin release/ or the response of the ovaries to these hormones.
Where are ADH and oxytocin synthesised?
By neurones of the hypothalamus, supraoptic nuclei and paraventricular nucleus. The hormones are synthesised as inactive hormones, transported along the hypothalamico-neurohypophyseal tract to the POSTERIOR pituitary gland, where they are then stored and converted to their active form before secretion.
What does ADH do?
ADH decreases the urinary output by binding to the V2 receptors in the basolateral membrane of the cells in the distal tubule and collecting ducts of the nephron. It causes an increase in the insertion of water channels into the lumenal membrane.
Which drugs increase the action of ADH (vasopressin)?
Non-steroidal anti-inflammatory drugs and carbamazepine.
Which drugs decrease the action of ADH (vasopressin)?
Lithium, colchicine, vinca alkaloids.
What are the symptoms of a sellar mass?
Most likely would be a pituitary adenoma. Would cause visual impairment, diplopia (double vision), headache. Hormonal abnormalities could mean hypogonadism in men and women.
How would you diagnose a anterior pituitary adenoma?
MRI, visual field assessment.
What biochemical tests would you perform to test function of the anterior pituitary gland?
TSH & T4 Cortisol LH & FSH A prolactin (PRL) test Testosterone / “Periods” 0900 am
