T3 Hypothalamus-Pituitary Axis

portal system - purpose

limited space

which hormone is present in bloodstream if connection between hypothalamus and pituitary gland is disrupted

prolactin

only negative regulation in hypothalamus pituitary axis

dopamine inhibit prolactin

ADH (vasopressin) - function

water reabsorption in kidney, vasoconstriction of arterioles

oxytocin - function

uterine contractions, milk ejection

what hormone is important for growth during infantile and early childhood

thyroid hormone (need iodine) for brain development

what hormone is important for growth during childhood and puberty

growth hormone

growth hormone regulation

stimulated by GHRH, inhibited by somatostatin, negative feedback by IGF-1

GH - effects

fat mobilization, increased blood glucose, increased growth

what stimulates GH secretion

decreased blood glucose, fasting, strenous exercise, deep sleep

what inhibits GH secretion

increased blood glucose, aging, obesity, IGF-1

excessive growth hormone secretion in children

gigantism, excessive linear skeletal growth due to high IGF-1

excessive growth hormone secretion after growth plates closed

acromegaly, growth of hand, feet, jaw, organs, but not height

how to test for acromegaly

impaired glucose suppression test (GH remain high after glucose consumption), insulin resistance

acromegaly - complications

GH remains high all the time, comorbidity of diabetes, insulin weaken (glucose intolerance), cardiomyopathy and congestive heart failure from ventricular hypertrophy

growth hormone deficiency - short stature

normal proportions but with increased weight

prolactin - effects

inhibit second birth for a few months after delivery, suppressed GnRH

prolactin - stimulated by

TRH (hypothyroidism)

hyperprolactinemia - effects

prolactinoma (compress optic chiasm > peripheral blindness), fertility problems, galactorrhea, amenorrhea, sexual dysfunction, osteoporosis