Hypophysis- Anterior Pituitary Prof. K. Sivapalan

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. 08-01-14 Anterior Pituitary

Development. Rathke's pouch- anterior pituitary. Floor of the third ventricle- posterior pituitary. 08-01-14 Anterior Pituitary

Anterior Pituitary. [Adenohypophysis] 08-01-14 Anterior Pituitary

Blood supply Anterior lobe: superior hypophysial artery and Hypothalamic Hypophysial Portal system from hypothalamic nuclei. 08-01-14 Anterior Pituitary

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. 08-01-14 Anterior Pituitary

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. 08-01-14 Anterior Pituitary

TSH Glycoprotein, 30000mw, a and b chains. Control- TRH Action on thyroid gland. 08-01-14 Anterior Pituitary

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. 08-01-14 Anterior Pituitary

08-01-14 Anterior Pituitary

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 08-01-14 Anterior Pituitary