On Rounds: 1000 Internal Medicine Pearls by Landsberg Lewis

Author:Landsberg, Lewis
Language: eng
Format: epub
ISBN: 978-1-4963-2923-3
Publisher: LWW
Published: 2015-07-14T16:00:00+00:00

ANTERIOR PITUITARY

Prolactin

High levels of prolactin are associated with hypogonadism in men and women. Galactorrhea occurs in women if the breast has had the appropriate endocrine priming.

Hyperprolactinemia may be caused by tumor (prolactinoma), lesions that disrupt the pituitary stalk, or drugs.

The highest circulating prolactin levels (over 100 μg/L) are caused by adenomas of the anterior pituitary. Many drugs produce modest prolactin elevations but neuroleptic agents that antagonize dopamine (DA) are the most common culprits.

Hypothyroidism may also be associated with elevations in prolactin that fall with appropriate treatment.

Prolactin is the only anterior pituitary hormone that is under tonic inhibition. DA, elaborated in hypothalamic regulatory neurons, inhibits the release of prolactin from the lactotropes of the anterior pituitary.

Lesions affecting the pituitary stalk disrupt the tonic inhibition imposed by DA resulting in enhanced secretion of prolactin.

Drugs that block the action of DA result in hyperprolactinemia. Dopaminergic agonists are useful in treating pituitary adenomas secreting prolactin.

Kallmann syndrome refers to a specific subset of patients with hypogonadotropic hypogonadism and anosmia (absent sense of smell).

In this syndrome luteinizing hormone (LH) and follicle stimulating hormone (FSH) are deficient due to a failure of the hypothalamus to produce gonadotropic-releasing hormone, which normally regulates the secretion of LH and FSH. Although it occurs in males and females it has a strong male predominance. The anosmia reflects poor development of the olfactory bulb. Hypogonadotropic hypogonadism also occurs with a normal sense of smell, but Kallmann syndrome refers specifically to the form with anosmia.

The presence of anosmia can be elicited by the question: have you ever smelled bacon cooking? (Almost everybody has!)

The disease is characterized by the combination of low gonadal hormones with low LH and FSH levels. Puberty is delayed and incomplete, testes are very small, secondary sex characteristics are absent or poorly developed, and in females presentation is frequently with primary amenorrhea.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.