522 Obstetrics and Gynecology Board Review •••
❍ What is the half-life of LH?
20 minutes.
❍ What is necessary for midcycle LH surge?
Increase in estradiol levels above critical concentration and duration (200 pg/mL for 48 hours).
The concentration of FSH is greater than LH.
❍ What cells within the pituitary secrete prolactin?
Lactotrophs.
❍ What is the function of prolactin?
It initiates and sustains lactation by the breast glands and it may influence synthesis and release of progesterone by
the ovary and testosterone by the testis.
❍ What inhibits the release of prolactin?
Dopamine.
❍ What is the main physiological stimulus for prolactin release?
Suckling of the breast.
❍ How do drugs such as metoclopramide, haloperidol, chlorpromazine, and reserpine enhance prolactin
secretion?
By interfering with release of dopamine into the pituitary portal circulation.
❍ What are the signs and symptoms of a pituitary neoplasm related to enlargement of the gland?
Visual field defects (bitemporal hemianopsia), abnormal extraocular muscle movements, and occasionally
spontaneous CSF rhinorrhea.
❍ What tests are used to determine gonadotropin deficiency?
Simultaneous measurement of FSH, LH, and gonadal steroids.
❍ What does low circulating gonadal steroid levels associated with an inappropriately low gonadotropin level
suggest?
A hypothalmic or pituitary disturbance.
❍ What is Sheehan syndrome?
Postpartum infarction and necrosis of the pituitary.
❍ What are the main clinical features of Sheehan syndrome?
(1) Postpartum failure to lactate.
(2) Postpartum amenorrhea.
(3) Progressive signs and symptoms of adrenal insufficiency and hypothyroidism.