Question

The posterior pituitary gland isn't a 'true' endocrine gland because
(A) It is under the regulation of the hypothalamus
(B) It secretes enzymes
(C) It is provided with a duct
(D) It only stores and releases hormones

Answer 1

Hint: The posterior lobe does not produce hormones by itself, this is performed by nerve cells in the hypothalamus but it works out release them into the circulation. The hormones of the pituitary gland send signals to other endocrine glands to facilitate or hinder their hormone production.

Complete answer:
The posterior pituitary (or neurohypophysis) is the hindmost lobe of the pituitary gland. The posterior pituitary is not glandulous as is the anterior pituitary. Rather, it is largely a batch of axonal projections from the hypothalamus that terminate behind the anterior pituitary and serve as an area for the secretion of neurohypophysial hormones (oxytocin and vasopressin) immediately into the blood.
Hormone secretion:
Two hormones are secreted by the posterior pituitary: oxytocin and vasopressin. These hormones are produced in the hypothalamus and circulated in the posterior pituitary. After generation, they are reserved in neurosecretory vesicles regrouped into Herring bodies before being discharged in the posterior pituitary through the bloodstream.
> Option (A) It is under the regulation of the hypothalamus: It is not a correct option
> Option (B) It secretes enzymes: The posterior pituitary lobe only decreases two main hormones that are oxytocin and vasopressin so this option is not correct.
> Option (C) It is provided with a duct: It is not provided with any duct as the posterior pituitary lobe is an extension of the hypothalamus. So, this option is also not correct.
> Option (D) It only stores and releases hormones: The posterior pituitary does not synthesize any kind of hormone. This lobe only reserves and discharges the hormone of the hypothalami like ADH and oxytocin.

Thus, the correct option is option D- it stores only and releases hormones.

Note:
The posterior lobe of the pituitary gland develops as an extension of the hypothalamus. As such, it is not competent in producing its hormones; instead, it reserves hypothalamic hormones for later discharge into the systemic circulation.