Question

Andre the Giant had a somatotropinoma, which is a tumor that secretes too much hormone on it’s own (without the need of outside stimulation). Where would this tumor be located and what hormone is being secreted from this tumor (2 pts)? What hormone normally stimulates somatotroph cells (1 pts)? What happens next in this pathway (continue explaining the pathway as if there wasn’t a tumor) (5 pts)? What negative feedback should be affecting the somatotropinoma (3 pts), and why might it not be working (2 pts)? Why is this condition dangerous if not treated (2 pts)? One of the treatments for this type of tumor is somatostatin (SS), which actually also affects another pituitary pathway. What pathway also responds to SS, and specifically HOW is that pathway affected (2 pts)? Based on this information, what other hormonal disorders can SS be used to treat (note, we’re not asking about treatment of the somatotropinoma in this question) (1 pt)? 2 pts for essay formatting, grammar, spelling.

Answer 1

A. Where would somatotropinoma tumor be located and what hormone is being secreted from this tumor ?

somatotropinoma tumor is located in the pituitary gland that is in the cranial cavity in a groove known as the sella turcica. Somatotrophs the growth hormone (GH) is secreted from this hormone.

B. What hormone normally stimulates somatotroph cells?

Growth hormone-releasing hormone (GHRH) which is a hypothalamic peptide normally stimulates somatotroph cells.

C. What happens next in this pathway (continue explaining the pathway as if there wasn’t a tumor)?

GH secretion occurs under the control of two hypothalamic hormones: GH-releasing hormone (GHRH), and somatostatin. GHRH stimulates GH secretion and somatostatin inhibits GH secretion. GHRH interacts with a G protein-coupled receptor (GHRHR) in somatotroph cells to activate the cyclic AMP signalling pathway. This leads to the release of GH. Once released into the circulation, GH binds to cell-surface GHR in target tissues. Binding leads to activation of Janus kinase 2 that in turn promote growth via the synthesis and secretion of endocrine peptide hormone known as Insulin-like Growth Factor-1 (IGF-1).

D. What negative feedback should be affecting the somatotropinoma, and why might it not be working? Why is this condition dangerous if not treated?

Short loop feedback should be affecting the somatotropinoma. Short loop feedback is a hormone providing negative feedback to the hypothalamus, inhibiting the secretion of the releasing hormone. If the negative feed is not working the GHRH stimulates the continuous secretion of somatotrophs and excess secretion in children leads to gigantism and adults results in acromegaly.

E. What pathway also responds to SS, and specifically.HOW is that pathway affected?

Inhibiting the release of growth hormone GHRH

F. What other hormonal disorders can SS be used to treat?

Tumors secreting vasoactive intestinal peptide.

Carcinoid tumors.

Glucagonomas