WEEK 5 Flashcards
What hormones does the anterior lobe of the pituitary gland produce and secrete?
Adrenocorticotropic Hormone (ACTH) Thyroid Stimulating Hormone (TSH) Growth Hormone (GH) Follicle Stimulating/Luteinising (Gonadotropic) Hormones (FSH/LH) Prolactin
What hormones are stored and secreted into the bloodstream from the posterior lobe of the pituitary gland?
ADH (anti-diuretic hormone)/Vasopressin
Oxytocin
Where are the hormones stored and secreted into the bloodstream via the posterior lobe of the pituitary gland produced?
Supraoptic and Paraventricular nuclei in the hypothalamus
How is hypothalamus activity regulated?
Hormone-mediated signals (negative feedback) and neural inputs
Other than endocrine function, what other functions of the hypothalamus are there?
Homeostatic processes such as maintenance of body temperature, thirst and food intake
What is the process of hormone secretion into the bloodstream via the anterior lobe of the pituitary gland?
Neurosecretory cells produce hypothalamic-releasing and hypothalamic-inhibiting hormones which are secreted into the hypophyseal portal vessels which travel through the tuberoinfundibular tract (to ant. lobe), causing stimulation or inhibition of hormone production and secretion from the anterior lobe into the bloodstream
What is the process of hormone secretion into the bloodstream via the posterior lobe of the pituitary gland?
Supraoptic and paraventricular nuclei in the hypothalamus produce ADH and oxytocin, these hormones move down axons to axon endings in the hypothalamo-hypophyseal tract and are stored in the posterior lobe until secretion from the axon endings into the bloodstream
What is the name of the stalk that connects the hypothalamus and pituitary gland?
Infundibulum
Which hormones regulate Growth Hormone production and secretion from the PG?
Growth Hormone Releasing Hormone (GHRH)
Somatostatin - INHIBITS
Which hormone regulates FSH/LH production and secretion from the PG?
Gonadotropin Releasing Hormone (GnRH)
Which hormone regulates ACTH production and secretion from the PG?
Corticotropin Releasing Hormone (CRH)
Which hormone regulates TSH production and secretion from the PG?
Thyrotropin Releasing Hormone (TRH)
Which hormone regulates Prolactin production and secretion from the PG?
Dopamine - INHIBITS
Describe Growth Hormone (GH)
Hormone released throughout life
Pulsatile (peaks and troughs)
Stimulated by hypoglycaemia, exercise and sleep, Suppressed by hyperglycaemia
Effects are mediated by IGF-1 (insulin-like growth factor)
Release stimulated by GHRH, inhibited by somatostatin
What are the effects of GH?
Linear growth in children Acquisition of bone mass Stimulates: Protein synthesis, Lipolysis, Glucose metabolism Regulates body composition Physiological well-being
Describe Follicle Stimulating Hormone (FSH)/Luteinising Hormone (LH)
Release stimulated by GnRH which increases in production at around 8y/o
FSH and LH trigger testosterone production in testes and oestrogen production in ovaries
What are the effects of FSH/LH?
Testosterone production: Male secondary sex characteristics Spermatogenesis Oestrogen production: Female secondary sex characteristics Folliculogenesis
Describe Prolactin
Essential for lactation
Levels dramatically increase in pregnancy and breast-feeding
inhibits gonadal activity through central suppression of GnRH (decreasing FSH/LH)
Inhibited by dopamine
Describe the hypothalamic-pituitary-adrenal axis
CRH secreted from hypothalamus, ACTH secreted from anterior pituitary gland, cortisol secreted from adrenal glands
What are the effects of cortisol?
Regulates glucose levels
Increases body fat
Helps body defence against infection
Helps body respond to stress
What change to the adrenal glands is seen due to ACTH excess?
Hyperplasia
What change to the adrenal glands is seen due to ACTH deficiency?
Atrophy
What is the effect of TSH?
Secretion of T3 and T4 hormones from the thyroid gland
What negative feedback is received in the hypothalamic–pituitary–thyroid axis?
Secretion of TRH is inhibited by T3
Secretion of TSH is inhibited by T3 and T4
Describe ADH/Vasopressin
Polypeptide synthesised in supraoptic and paraventricular nuclei of the hypothalamus
Primary determinant of the rate of free water excretion
Describe the process of ADH/Vasopressin on the rate of free water excretion
Hormone augments water permeability of the luminal membranes of cortical and medullary collecting tubules via opening of aquaporins (H20 channels), resulting in reabsorption of water into the blood
What are the major stimuli for ADH secretion?
Hyperosmolarity and effective circulating volume depletion
Describe the negative feedback loop of osmoregulation in response to increased plasma osmolarity/decreased effective circulating volume
1) Increased thirst, increased water intake, increased water retention, decreased plasma osmolarity and increased effective circulating volume, decreased thirst
2) increased ADH secretion, decreased water excretion, increased water retention, decreased plasma osmolarity and increased effective circulating volume, decreased ADH secretion
What is Oxytocin and what are it’s effects
Hormone under positive feedback
Stimulates contraction of smooth muscle of the breast and uterus-has role in milk ejection reflex and parturition (birth)->synthetic oxytocin can be given to induce labour
What do the main manifestations of pituitary disease relate to?
Mass effects from (para)sellar lesions
What are the 3 types of mass effects that result from pituitary disease?
Neurological
Visual
Hypopituitarism
What are the mass effects relating to neurological and visual changes?
Headaches Hypothalamic damage, brain damage III, IV, V, VI nerve damage Optic (II) nerve damage CSF leak
What are the main causes of hypopituitarism?
Pituitary/Parapituitary tumours
Radiotherapy
Pituitary infarction (apoplexy), Sheehan’s syndrome
Infiltration of the pituitary
Trauma
Isolated hypothalamic releasing hormone deficiency
What is the main manifestation of GH deficiency in children?
Poor growth
What are the manifestations of GH deficiency in adults?
increased abdominal fat, decreased lean body mass
impaired lipid profile
decreased muscle strength and exercise quality
impaired cardiac function
decreased bone mineral density
impaired psychological well-being
How would you diagnose GH deficiency?
GH stimulation tests (Insulin tolerance test, Glucagon, GHRH + arginine)
IGF-1 test
What is the treatment for GH deficiency?
Hormone replacement mimicking physiology-injections at night
What is the main manifestation of FSH/LH deficiency in children?
Delayed puberty
What are the manifestations of FSH/LH deficiency in men?
Decreased libido, impotence, infertility, decreased secondary sex features
Decreased muscle mass and strength, decreased mood and well-being, osteoporosis and anaemia
What are the manifestations of FSH/LH deficiency in women?
Decreased libido, menstrual disorders, infertility, dyspareunia, osteoporosis, premature atherosclerosis
How would you diagnose FSH/LH deficiency in men?
Measure FSH/LH levels and morning testosterone (increased levels in morning)
How would you diagnose FSH/LH deficiency in women?
Measure FSH/LH levels and check oestradiol levels + menstrual history
What is the treatment for FSH/LH deficiency?
Hormone replacement-testosterone/oestrogen
What is the result of hypopituitarism?
Pituitary hormone deficiency
What are the manifestations of ACTH deficiency?
Fatigue, weakness, nausea/vomiting, anorexia, weight loss, hypoglycaemia, hypotension, anaemia
How would you diagnose ACTH deficiency?
9am serum cortisol and ACTH levels
What are three dynamic tests for ACTH deficiency diagnosis?
Short synacthen test
Insulin tolerance test
Glucagon test
What is the treatment for ACTH deficiency?
Hormone replacement (Corticosteroids)-approximate diurnal rhythm
What are the manifestations of TSH deficiency?
(similar to hypothyroidism)
Fatigue, weakness, cold tolerance, bradycardia, inability to lose or gain weight, puffiness, pale/dry skin, constipation
How would you diagnose TSH deficiency?
Measure TSH, fT3 and fT4 levels
What is the treatment for TSH deficiency?
Hormone replacement (levothyroxine)
What is the cause of Central Diabetes Insipidus?
Deficient ADH secretion
What are the different causes of ADH secretion deficiency->Central Diabetes Insipidus?
Idiopathic (autoimmune destruction of hormone secreting cells) Familial Tumours Neurosurgery/Trauma Infiltrative disorders Infections Hypoxic encephalopathy/severe ischaemia
What are the manifestations of ADH deficiency?
Polyuria (excessive urination)
Polydipsia (excessive thirst)
Nocturia (waking up at night to urinate)
What are the major causes of polyuria?
Diabetes Mellitus and renal failure (osmotic diuresis-urine not diluted clear due to presence of unwanted substances)
Primary polydipsia
Diabetes insipidus
How would you diagnose ADH deficiency?
Measure urine output, osmolalities (plasma, urine), blood electrolytes/glucose/urea/creatinine
Water deprivation test
What is the treatment for ADH deficiency?
ADH analogues
What are Functioning Pituitary Adenomas?
Benign tumours which hypersecrete one or more hormones
What is GH hypersecretion acromegaly?
Hypersecretion of GH by pituitary adenoma, GH constantly secreted (no troughs)
What are some of the vast manifestations of acromegaly?
Large hands and feet
Prognathism (protruding jaw)
Weight gain
Goitre
How would you diagnose GH hypersecretion acromegaly?
Oral glucose tolerance test
IGF-1 test
Pituitary imaging
What is the treatment for GH hypersecretion acromegaly?
Pituitary surgery
Medical treatment (GH receptor antagonists, dopamine agonists, somatostatin analogues)
Radiotherapy
What are the general types of many causes of high prolactin?
Physiological
Drugs
Pathological
What is a Prolactinoma?
A benign tumour secreting large amounts of prolactin
What are the manifestations of a prolactinoma?
Hypogonadism
Galactorrhoea (milky nipple discharge)
Mass effects
How would you diagnose a prolactinoma?
Exclude other causes of high prolactin
Pituitary imaging
What is the treatment for a prolactinoma?
Medical treatment (dopamine agonists)
Surgery-transsphenoidal
Radiotherapy
What is a TSHoma (thyrotropinoma)?
A pituitary tumour causing hypersecretion of TSH
What are the manifestations of a TSHoma?
Thyrotoxicosis Mass effects (tachycardia, arrhythmia, increased body temp.)
What is the treatment for a TSHoma?
Surgery
Medications
Radiotherapy
What is an FSHoma?
A pituitary tumour causing hypersecretion of FSH
What are the manifestations of an FSHoma in men?
Testicular enlargement
Infertility
Mass effects
What are the manifestations of an FSHoma in women?
Menstrual irregularities
Ovarian hyperstimulation
Mass effects
How would you diagnose a TSH/FSHoma?
Hormonal tests
Pituitary imaging
What is the treatment for an FSHoma?
Surgery
Radiotherapy
