Lecture 11- Organisation Of The Endocrine System

Question 1

Overview

Answer 1

Neuroendocrine system= controlled by the pituitary coordinates body functions by transmitting messages between individual cells + tissues
-endocrine system= releases hormones into the bloodstream= carries these chemical messengers to target cells throughout the body

-drugs that mimic/block the effects of the hypothalamic + pituitary hormones= pharmacological applications in 3 areas
*as replacement therapy for hormone deficiency states
*as antagonists for diseases that result from excess production of pituitary hormones
*diagnostic tools for identifying several endocrine abnormalities

• hormones of the anterior pituitary are regulated by neuropeptides that are either releasing/inhibiting factors or hormones

Question 2

Anterior pituitary hormones: adrenocorticotropic hormone

Answer 2

Adrenocorticotrophic hormone= anterior pituitary secretion that controls the synthesis and release of the glucocorticoids of the adrenal cortex

Question 3

Anterior pituitary hormones: growth hormone

Answer 3

-growth hormone= secreted by the somatotroph cells of the anterior pituitary
-secretion is high in the new born < at 4 years= then maintained until after puberty -> further decline after
-main effect is to stimulate normal growth; affects many tissues acting in conjunction with other hormones secreted from the thyroid, gonads + adrenal cortex

Question 4

Clinical uses of growth hormone

Answer 4

-deficiency of growth hormone= pituitary dwarfism
-used therapeutically in patients (often children) with growth hormone deficiency
-satisfactory linear growth= achieved by giving growth hormone subcutaneously; 6-7x per week = successful if started early
-excessive production of growth hormone in children= gigantism
-excessive production in adults= acromegaly (enlargement of facial structures + hands/feet) -> result of a benign pituitary tumour

Question 5

Anterior pituitary hormones: Gonadotropins

Answer 5

*follicle stimulating hormone (FSH)
*luteinising hormone (LH)
*human chorionic gonadotropin (hCG) similar to LH
^gonadotropins
Regulation of the hormones depends on the agents
Use in treatment of infertility in men + women= stimulates spermatogenesis in men + induces ovulation in women

*FSH;
-females= ovarian follicular development
-males= spermatogenesis

*LH;
-females= stimulates oestrogen + progesterone production
-males= production of testosterone by the leydig cells

Question 6

Posterior pituitary hormones

Answer 6

*oxytocin + *antidiuretic hormone (vasopressin)
-hormones of the posterior pituitary= not regulated by releasing hormones
-synthesised in the hypothalamus -> transported to the posterior pituitary + released in response to specific physiologic signals; e.g. high plasma osmolarity/parturition
*oxytocin + ADH= susceptible to proteolytic cleavage and are given parenteral
-short half-lives

Question 7

Posterior pituitary hormones; oxytocin

Answer 7

-used in obstetrics= stimulates uterine contractions to induce/reinforce labour (uterus at term is highly sensitive to this hormone)
-given by IV to induce labour, causes regular coordinated contractions
-excessively high doses= cause sustained contractions that interfere with blood flow through the placenta and cause foetal distress/death
-promote ejection of breast milk

Pharmacokinetics;
-can be given by IV injection/ IM but mainly IV

Unwanted effects;
-dose-related hypotension
-ADH-like effect on water excretion by the kidney= water retention

Question 8

Posterior pituitary hormones; Antidiuretic hormone (ADH)

Answer 8

-has both antidiuretic + press or effects
-stimuli to ADH release;
*increase in plasma osmolality (produces sensation of thirst)
*decrease in circulating blood volume (hypovolaemia)

*diabetes insipidus= large volumes of dilute urine are produced because ADH secretion is reduced/absent or reduced sensitivity of the kidney to the hormone

*non-steroidal anti-inflammatory drugs and *carbamazepine increase + *lithium, *colchicine + *vinca alkaloids = decrease ADH effects

-non-renal actions= ADH causes contraction of smooth muscle; in the cardiovascular system

Question 9

Posterior pituitary hormones; ADH

Answer 9

Clinical uses;
-treat diabetes insipidus
-used as a vasoconstrictor= controlling bleeding
-short duration of action; analogues were developed to increase duration of action
*desmopressin
*terlipressin

Pharmacokinetics;
*vasopressin= rapidly eliminated with a plasma half-life of 10 mins and a short duration of action
*desmopressin= less subject to metabolism and plasma half-life is 75 mins