What is the function of the pituitary gland?

Concept

The pituitary gland (hypophysis) is a pea-sized endocrine gland lying in the sella turcica at the base of the brain, under hypothalamic control. It is called the master gland because it works on two levels at once. Its tropic hormones — FSH, LH, ACTH and TSH — stimulate other endocrine glands (gonads, adrenal cortex, thyroid), while its remaining secretions act directly on body tissues: growth hormone on growth-capable tissues, prolactin on the mammary gland, and from the posterior lobe ADH (vasopressin) on the kidney tubule and oxytocin on uterine and mammary smooth muscle.

So a "what does the pituitary do" item is not settled by picking one organ system. Trace each listed activity back along its hormone axis — noting whether the gland acts directly on the tissue or indirectly through a target gland — and then count how many of the listed activities the pituitary reaches at all.

Application to this question

Tracing each listed activity along its axis:

• Development of sex organs in males — the anterior pituitary secretes the gonadotropins FSH and LH. LH stimulates the Leydig (interstitial) cells of the testis to secrete testosterone; that testicular testosterone, and the dihydrotestosterone derived from it, then develops the male reproductive organs and secondary sexual characters, while FSH acts on Sertoli cells to sustain spermatogenesis. Control here is therefore indirect — it runs down the hypothalamic–pituitary–gonadal axis — but the pituitary is the step without which the axis does not operate.

• Stimulation of growth in all organs — growth hormone (somatotropin) from the anterior pituitary promotes body growth largely through liver-derived IGF-1, acting on bone, cartilage, muscle and viscera; that is, on growth-capable tissues broadly, which is what the exam phrase "all organs" is shorthand for rather than a literal claim of uniform growth in every organ. Deficiency in childhood causes pituitary dwarfism; excess causes gigantism in children and acromegaly in adults.

• Regulation of sugar and salt levels — ACTH from the anterior pituitary drives the adrenal cortex to secrete cortisol, which raises blood glucose mainly by promoting gluconeogenesis and reducing peripheral glucose uptake; and ADH from the posterior lobe controls water reabsorption in the kidney tubules, setting plasma osmolality and hence the concentration of salt in the body fluids. Note the level of this claim: pancreatic insulin and glucagon are the principal regulators of glucose, and aldosterone through the renin–angiotensin–aldosterone system is the principal regulator of sodium balance, so the pituitary influences both variables rather than owning either.

Read at the level the exam intends, each of the three listed activities is reached by a pituitary hormone; and even on the strictest reading, male reproductive development and general body growth are unambiguously pituitary functions. Either way more than one of the listed activities belongs to this gland, so no single listed activity is a complete statement of what it does.

Cross-check

Now compare the composite choices with the traced hormone axes. ‘None of the above’ would require the pituitary to reach none of reproduction, growth, or metabolic and water–salt balance, which FSH/LH, GH, and ACTH/ADH contradict. Because this source paper uses a single-correct format with composite choices, selecting one true constituent statement would ignore that at least one other listed activity also applies. ‘More than one of the above’ is therefore the most complete offered response and the keyed answer.

The anterior-lobe mnemonic FLAT PiG — FSH, LH, ACTH, TSH, Prolactin, GH — is by itself enough to show that the pituitary spans reproduction, metabolism and growth simultaneously.