54

CASE 54


A 36-year-old woman presented to her family practitioner with complaints of weight gain, muscle weakness, ruddy complexion (plethora), a rounded face (“moon” face), and streaks on her skin (striae). She also informed her physician that she was concerned about her elevated blood pressure after a recent self-administrated measurement at the local drugstore. Dexamethasone suppression tests indicated a pituitary cause of excess ACTH and a MRI study demonstrated an adenoma of the pituitary gland. The patient was diagnosed with an ACTH-secreting pituitary gland tumor (Cushing’s disease).



WHAT IS THE ARTERIAL SUPPLY TO THE PITUITARY GLAND?


The pituitary gland is supplied by the following arteries (Fig. 7-14):


• Pair of inferior hypophyseal arteries

• Several pairs of superior hypophyseal arteries

image

FIGURE 7-14 Illustration of the circulation of the pituitary gland.


(Gartner L and Hiatt J: Color Textbook of Histology, 2e. WB Saunders, 2001. Fig. 13-2.)


Each inferior hypophyseal artery arises from each internal carotid within the cavernous sinus. The superior hypophyseal arteries issue from multiple parent vessels. These are the supraclinoid segments of the internal carotid arteries and the anterior and posterior cerebral arteries.



WHERE ARE ACTH-SECRETING CELLS LOCATED IN THE PITUITARY GLAND AND HOW ARE THEY DESCRIBED HISTOLOGICALLY?


The cells responsible for secreting ACTH are called corticotrophs. Corticotrophs are observed in the pars distalis of the anterior pituitary (also known as the adenohypophysis).


Histologically, the cells of the adenohypophysis are classified on the basis of their staining characteristics. The resident cells of the adenohypophysis are:


• Acidophils, which have an affinity for acid dyes

• Basophils, which react with basic dyes

• Chromophobes, which are cells that fail to react with dyes

Corticotrophs are a type of basophil. Typically, basophils are located at the periphery of the pars distalis. At the ultrastructural level, corticotrophs exhibit an eccentric nucleus in a cell that is round to oval in shape. The organelles are not well developed and the cytoplasm contains secretory vesicles (250–400 nm in diameter). The secretory vesicles are known to contain several hormones:


• ACTH

• Pro-opiomelanocortin

• Melanocyte-stimulating hormone

• Endorphins

• Lipotropin


WHAT ARE THE PATHOLOGIC CHARACTERISTICS OF THE PITUITARY GLAND IN CUSHING’S DISEASE?


The pathologic characteristics of the pituitary gland in Cushing’s disease are:


• There is an increase in the number of basophils in the pars distalis. This increase can be in the form of a discrete adenoma or hyperplasia that is diffusely distributed throughout the gland.

• The basophilic nature of the corticotrophs is altered by the excessive stimulation of glucocorticoids. The normal basophilic granulated appearance of the corticotroph’s cytoplasm is replaced by a uniform, lightly basophilic substance. This lightly basophilic feature is due to an accumulation of keratin, a type of intermediate filament, in the cytoplasm. This alteration in the cytoplasm is termed Crooke’s hyaline change.

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Jun 16, 2016 | Posted by in ANATOMY | Comments Off on 54

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