Endocrine system II - Pituitary hormones Flashcards
Pituitary Gland
Anterior (glandullar cells)
Adenohypophysis (gland)
Posterior (neural)
Neurohypophysis
Hypothalamus-Pituitary
Cell bodies and the neurons responsible for the secretion of hypothalamic releasing factors (hormones)
Anterior
Hypothalamus-Pituitary
Releasing factors pass along the portal vessels to reach capillary bed of the anterior pituitary, to control secretion of anterior pituitary hormones
Posterior
Hypothalamus-Pituitary
Paraventricular (PVN) and supraoptic (SON) nuclei, and the neurons carrying oxytocin and ADH (vasopressin) to the posterior pituitary, where they are stored/ released
Anterior pituitary hormones
somatotrophs somatotropin GH
corticotrophs corticotropin ACTH
thyrotrophs thyrotropin TSH
gonadotrophs gonadotropins LH, FSH
Pituitary Gland
Pituitary tumours are mostly benign and
slow-growing
Over/under production of hormones (Hyper/Hypo)
Local effects: pressure on surrounding structures
– headaches, visual disturbances
Somatotropin, GH
It is stored in the cells as granules. Growth hormone production is pulsatile
Peptide hormone: 21.5 K Da single-chain polypeptide (190 AA) with 2 disulphide bridges)
Major role in growth (linear) & metabolism
Drop in blood glucose
GH, Function
Protein synthesis increases in muscle, so does gluoconeogenesis in liver and blood glucose increases
Direct GH
on metabolism
Indirect GH
growth
Insulin-like growth factors (somatomedins) from liver
Whta influences GH release?
Blood glucose, free fatty acids and amino acid levels
List GH, diseases
a) Dwarfism (stunted growth)
b) Gigantism in children/Acromegaly in adults
a) Dwarfism (stunted growth)
Psychological changes
Malaise, excessive tiredness, anxiety and depression
Osteoporosis
Poor muscular tone, decrease in lean body mass
Impaired hair growth
Increase in adipose tissue (especially around the waist)
b) Gigantism in children/Acromegaly in adults
coarsening of facial features
enlarged hands and feet
headaches, vision disturbance
sleep apnoea, general tiredness
hypertension, cardiomegaly
glucose intolerance (diabetes)
irregular or loss of periods (females); impotence (males)
Thyroid hormones” – thyroxine (T4) and tri-iodothyronine (T3) - calcitonin & parathyroid hormone (PTH)
Calcitonin produced by parafollicular C cells (acts to reduce plasma calcium)
PTH is produced by parathyroid glands (4x small glands located in posterior surface of thyroid gland, they increase plasma calcium (oppose calcitonin effect)
one iodination = MONO-iodotyrosine
Tyrosine, iodinated at 3’ of ring = MIT
T3
active hormone
Synergistic effect with sympathetic/catecholamine
(T3 increase the expression adrenergic receptors)
Basal Metabolic Rate (BMR): Sugar, Fat, Protein
Growth & Development: CNS
T4
circulating as a pro hormone
Goitre – enlarged thyroid gland
DIFFUSE
NODULAR
DIFFUSE
Cause
Primary failure of thyroid gland
(~ 90%: Hashimoto’s thyroiditis)
Secondary to hypothalamic or ant. pituitary failure
Lack of dietary iodine (simple non-toxic goitre)
Drug-induced
(e.g. anti-thyroid drugs, lithium, amiodarone)
Radioactive iodine therapy, surgery
Thyroid hormone resistance
Plasma [ ] of hormones + Goitre present?
Less T3 and T4, more TSH, Yes
less T3 and T4, less TSH, No
less T3 and T4, more TSH, Yes
NODULAR
Cause:
Abnormal levels of thyroid-stimulating immunoglobulins
(Graves’ disease)
Secondary to excess hypothalamic or
ant. pituitary secretion
Hyper-secreting thyroid tumour
(Toxic multinodular goitre, toxic adenoma)
Iatrogenic causes (e.g. amiodarone, lithium)
Plasma [ ] of hormones + Goitre present?
^T3 and T4, low TSH, Yes
^T3 and T4, ^TSH, Yes
^T3 and T4, low TSH, Yes
What is T3 function?
BMR (basic metabolic rate);
Body core temperature
Sweating
Thermal discomfort
Appetite
Body weight
Bowels
Hyperthyroid
Heat intolerance
Weight loss
Diarrhoea
INCREASE in HR, MAP (palpation)
Hypothyroid
decrease
cold intolerance
decrease
weight gain
constipation
The function of T3 - growth and development: CNS
Anxiety, emotional, irritable, restless, tremor
Growth acceleration
Depression, confusion, poor memory, difficulty in concentrating Cretinism (perinatal)
Growth deficiency (childhood)
Dry skin, hoarse voice, menstrual problems
T3 ______ the expression adrenergic receptors
increases
[synergistic effect with sympathetic/catecholamine]
