Section X: Endocrinology and Metabolism

Section X: Endocrinology and Metabolism

All of the following hormones is produced by the anterior pituitary EXCEPT:

A. Adrenocorticotropic hormone

B. Growth hormone

C. Oxytocin

D. Prolactin

E. Thyroid-stimulating hormone

The answer is C. (Chap. 401e) Hormones produced by the anterior pituitary include adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin, and growth hormone. The posterior pituitary produces vasopressin and oxytocin. The anterior and posterior pituitary have a separate vascular supply, and the posterior pituitary is directly innervated by the hypothalamic neurons via the pituitary stalk, thus making it susceptible to shear stress–associated dysfunction. Hypothalamic control of anterior pituitary function is through secreted hormones; thus, it is less susceptible to traumatic injury.

A 45-year-old man reports to his primary care physician that his wife has noted coarsening of his facial features over several years. In addition, he reports low libido and decreased energy. Physical examination shows frontal bossing and enlarged hands. An MRI confirms that he has a pituitary mass. Which of the following screening tests should be ordered to diagnose the cause of the mass?

A. 24-Hour urinary free cortisol

B. Adrenocorticotropic hormone (ACTH) assay

C. Growth hormone level

D. Serum insulin-like growth factor-1 (IGF-1) level

E. Serum prolactin level

The answer is D. (Chap. 401e) Functional pituitary adenoma presentations include acromegaly, as in this patient; prolactinomas; or Cushing syndrome. Hypersecretion of growth hormone underlies this syndrome in patients with pituitary masses, although ectopic production of growth hormone, particularly by tumors, has been reported. Because growth hormone is secreted in a highly pulsatile fashion, obtaining random serum levels is not reliable. Thus, the downstream mediator of systemic effects of growth hormone, insulin-like growth factor-1 (IGF-1), is measured to screen for growth hormone excess. IGF-1 is made by the liver in response to growth hormone stimulation. An oral glucose tolerance test with growth hormone obtained at 0, 30, and 60 minutes may also be used to screen for acromegaly because normal persons should suppress growth hormone to this challenge. Serum prolactin level is useful to screen for prolactinomas, and 24-hour urinary free cortisol and ACTH assay are useful screens for Cushing disease.

Which of the following statements regarding the anatomy of the pituitary gland is true?

A. Growth hormone is derived from the precursor proopiomelanocortin (POMC).