1. Hypophysis- Anterior Pituitary
Prof. K. Sivapalan

2. Location. It is located in Sella Turcica, under Diaphragma Sella.
It weighs 0.5g.
In pregnancy it hypertrophies to 1g.
75% of the gland is anterior lobe- anterior pituitary.
25% is posterior pituitary.
Anterior Pituitary

3. Development. Rathke's pouch- anterior pituitary.
Floor of the third ventricle- posterior pituitary.
Anterior Pituitary

4. Anterior Pituitary. [Adenohypophysis]
Anterior Pituitary

5. Blood supply
Anterior lobe: superior hypophysial artery and Hypothalamic Hypophysial Portal system from hypothalamic nuclei.
Anterior Pituitary

6. ACTH
Single chain, 39 amino acids, parts resembling MSH and stimulates Melanocyte activity.
Half life- 3-4 minutes.
Regulation of secretion- studied under glucocorticoids.
ACTH and β-LPH- lipotropin are synthesized as one molecule and split before release.
Lipotropin resembles Endophins and Enkephalins which act like opiates.
?use in stress.
Anterior Pituitary

7. Gonodotrophins- FSH + LH.
FSH- follicular stimulating hormone.
Glycoprotein, 25000mw, a and b chains.
Action on testis and ovaries.
Secretion at puberty.
LH- Luteinizing hormone.
Glycoprotein, 40000mw, a and b chains.
Secretion starts at puberty.
Anterior Pituitary

8. TSH Glycoprotein, 30000mw, a and b chains. Control- TRH
Action on thyroid gland.
Anterior Pituitary

9. Prolactin. Structure- similar to GH. Human Prolactin- 198 amino acids.
Control- Prolactin Inhibiting Hormone (Dopamine, - only inhibitory factor from hypothalamus)
Chlorpromazine stimulates secretion by reducing Dopamine receptors.
Regulation-
exercise and stress- surgical or psychological.
stimulation of nipple by nerves to hypothalamus.
Anterior Pituitary

10.
Anterior Pituitary

11. Actions of Prolactin
Secretion of milk in breast prepared by estrogen, progesterone, growth hormone and corticoids.
At high concentrations, similar metabolic actions as Growth Hormone.
(Ejection of milk -by oxytocin)
Hyperprolactinaemia:
Inhibition of menstruation in females
Impotence and hypogonadism in males.
Mechanism not known. ? Inhibition of gonadotropins by nervous stimuli from breast or prolactin
Anterior Pituitary