Why two different stimuli to the somatotroph release more together than the sum of each, as the 1980s and 1990s work showed

Published 26 October 2026 · REVIVE LAB UAE Research Desk · 5 min read
Cyril Bowers and colleagues designed the first growth hormone-releasing peptides in the late 1970s and 1980s, before their receptor or its natural ligand ghrelin were known, and showed that they released growth hormone through a mechanism distinct from GHRH — raising intracellular calcium through a different G protein where GHRH raises cyclic AMP. Given together, the two produced a release greater than the sum of each alone, in animals and in humans, a synergy that became a standard observation in pituitary physiology and was later explained by the two receptors converging on the same cells with complementary second messengers and by the peptides also suppressing somatostatin. This is physiology of the somatotroph; it is not a statement about any combination of products.

Two receptors on one cell

The GHRH receptor is class B and works through Gs and cyclic AMP; the ghrelin receptor is class A and works through Gq, phospholipase C and calcium. Both pathways drive exocytosis of stored hormone, and activating both at once releases more than either, because they recruit different steps of the same release machinery. Ghrelin mimetics also act in the hypothalamus to release GHRH and inhibit somatostatin, which amplifies the effect in vivo.

The natural ligand of the second receptor, ghrelin, was found in 1999, two decades after the synthetic peptides.

What the observation established

That the somatotroph integrates at least two independent stimuli, that the magnitude of a growth hormone pulse depends on their coincidence, and that the pituitary has a release capacity well above what either stimulus alone produces. These findings shaped the understanding of pulsatility and of why fasting and sleep produce the pulses they do.

They did not establish any clinical use of combinations, and the one ghrelin mimetic approved as a medicine, macimorelin, is a diagnostic given alone.

Why it is here

Because this physiology is frequently invoked in connection with GHRH analogues and a reader should know what it is and what it is not. It describes physiology and no use of the pack or of any combination.

Tesamorelin is supplied by REVIVE LAB UAE for laboratory research use only, with identity by mass spectrometry and purity by HPLC for the batch. It is not for human or veterinary use, and no dosing, administration or protocol guidance is provided.

What it costs

FormatStrengthPriceAvailability
Tesamorelin Pack20 mgAED 1010In stock

Delivery is AED 40 flat and free on orders over AED 700. Payment is cash on delivery anywhere in the UAE, or USDT (TRC20) in advance, which takes 5% off the order total.

Frequently asked

Two receptors on one cell?

The GHRH receptor is class B and works through Gs and cyclic AMP; the ghrelin receptor is class A and works through Gq, phospholipase C and calcium. Both pathways drive exocytosis of stored hormone, and activating both at once releases more than either, because they recruit different steps of the same release machinery. Ghrelin mimetics also act in the hypothalamus to release GHRH and inhibit somatostatin, which amplifies the effect in vivo.

Does REVIVE LAB UAE provide dosing guidance?

No. REVIVE LAB UAE supplies research materials and provides no dosing, administration or protocol guidance of any kind. Every product is sold for laboratory research use only and is not for human or veterinary consumption.

How fast is delivery in the UAE?

Stock is held in Dubai. An order confirmed before 4 PM Dubai time is dispatched the same working day, reaching Dubai and Abu Dhabi the same day and the remaining emirates within 24 hours. Delivery is AED 40 flat and free over AED 700.

Tesamorelin Pack — in stock, dispatched from Dubai
HPLC-verified, lot certificate on every carton, 24-hour delivery nationwide. Browse the catalogue → All peptides UAE

Related reading

Supplied for laboratory research use only. Not for human or veterinary consumption. REVIVE LAB UAE provides no dosing, administration or protocol guidance.