Wednesday, June 12, 2024
HomePediatrics: General MedicinePediatric Hypopituitarism

Pediatric Hypopituitarism

Background

Hypopituitarism is a partial or complete insufficiency of pituitary hormone secretion that may derive from pituitary or hypothalamic disease. The onset can be at any time of life. The focus of this article is childhood-onset hypopituitarism. (See the image below.)

The left photograph shows an untreated 21-month-ol

The left photograph shows an untreated 21-month-old girl with congenital hypopituitarism. The right panel depicts the same child aged 29 months, following 8 months of growth hormone therapy.

View Media Gallery

Intrinsic pituitary disease, or any process that disrupts the pituitary stalk or damages the hypothalamus, may produce pituitary hormone deficiency. The clinical presentation of hypopituitarism may vary, depending on patient age and on the specific hormone deficiencies, which may occur singly or in various combinations. As a general rule, diagnosis of a single pituitary hormone deficiency requires evaluating the other hormone axes. (See Etiology, History, and Physical Examination.)

Pituitary gland development and physiology

The pituitary gland, located at the base of the brain, is composed of anterior (ie, adenohypophysis) and posterior (ie, neurohypophysis) regions. The anterior pituitary, an ectodermal structure that derives from the pharynx as the Rathke pouch, produces most of the gland’s hormones. The major biologically active hormones released into systemic circulation from the anterior pituitary include the following:

Growth hormone (GH)

Adrenocorticotropic hormone (ACTH)

Thyroid-stimulating hormone (TSH)

Luteinizing hormone (LH)

Follicle-stimulating hormone (FSH)

Prolactin (PRL)

The pathway from embryogenesis to the full differentiation of specific functional cell types within the pituitary is controlled by numerous genes that encode transcription factors. (See the diagram below.) Mutations in these genes are causes of congenital hypopituitarism and have specific pituitary hormone deficiencies associated with the involved gene. (See Etiology.)

Regulation of the development of the mammalian ant

Regulation of the development of the mammalian anterior pituitary gland by transcription factors. Following, inductive signals between the developing diencephalon and the oral ectoderm, early transcription factors guide the formation of rudimentary Rathke’s Pouch (rRP) and then subsequent gene regulatory pathways control the determination, proliferation, and differentiation events that establish the specialized hormone-secreting cells. AP = anterior pituitary, IP = intermediate pituitary, PP = posterior pituitary. Modified by S. Rhodes from Mullen, R.D., Colvin, S.C., Hunter, C.H., Savage, J.J., Walvoord, E.C., Bhangoo, A.P.S., Ten, T., Weigel, J., Pfäffle, R.W., and Rhodes, S.J. (2007). Roles of the LHX3 and LHX4 LIM-homeodomain factors in pituitary development. Mol. Cell. Endocrinol., 265-266: 190-195.

View Media Gallery

The anterior pituitary is primarily regulated by neuropeptide-releasing and release-inhibiting hormones produced in the hypothalamus. These regulatory hormones are transported to the anterior pituitary via the pituitary portal system circulation. The release-stimulating hormones produced by the hypothalamus include the following:

Growth hormone–releasing hormone (GHRH)

Corticotropin-releasing hormone (CRH)

Thyrotropin-releasing hormone (TRH)

Gonadotropin-releasing hormone (GnRH)

PRL secretion is distinct from that of the other anterior pituitary hormones, being inhibited by hypothalamic dopamine. In addition, antidiuretic hormone (ADH) produced in the hypothalamus acts synergistically with CRH to promote ACTH release.

A negative feedback loop occurs such that the hormones produced in the target glands feed back to inhibit the release of their respective regulatory pituitary and hypothalamic factors. For example, hypothalamic TRH stimulates TSH release, which in turn stimulates the thyroid gland, resulting in increased serum levels of thyroxine (T4) and triiodothyronine (T3). When they have reached sufficient levels, T3 and T4 suppress TRH and TSH release.

The posterior pituitary consists of neural tissue that descends from the floor of the third ventricle. In contrast to the anterior pituitary hormones, the posterior pituitary hormones (ie, ADH, oxytocin) are synthesized by cell bodies in the hypothalamus and transported along the neurohypophyseal tract of the pituitary stalk. Release of these hormones occurs in response to neurohypophyseal stimuli.

RELATED ARTICLES
- Advertisment -

Most Popular