An 8-Year-Old Boy Is Brought to the Physician by His

An 8-year-old boy is brought to the physician by his parents for short stature. Neither his clothing nor his shoe size has changed over the past year. He also frequently bumps into obstacles such as furniture and has headaches at night. He is always thirsty for cold water and has been urinating more frequently. Three years ago, he had an asthma attack that was treated with albuterol and a one-week course of steroids. His mother has Hashimoto's thyroiditis and had precocious puberty. His mother's height is 147 cm (4 ft 10 in) and his father's height is 160 cm (5 ft 3 in) . He is at the 5th percentile for height and 5th percentile for weight. His temperature is 37°C (98.6°F) , pulse is 98/min, respirations are 16/min, and blood pressure is 100/64 mm Hg. Examination shows a soft and nontender abdomen. The genitals and pubic hair are both Tanner stage 1. Axillary hair is absent. Patellar reflexes are 1+ bilaterally. From which of the following structures is this mass most likely derived?

A) Prolactin secreting cells of the anterior pituitary
B) Remnants of the Rathke pouch
C) Astrocytes
D) Arachnoid cap cells
E) Posterior pituitary cells