science

Gonadotropin

Gonadotropin is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Gonadotropin rather than just read about it. In short: Gonadotropins are glycoprotein hormones secreted by gonadotropic cells of the anterior pituitary of vertebrates. They are central to the complex endocrine system that regulates normal growth, sexual development, and reproductive function.

Key takeaways

Gonadotropin belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Gonadotropin to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Gonadotropin from memory before moving on to harder problems.

Reference excerpt

Gonadotropins are glycoprotein hormones secreted by gonadotropic cells of the anterior pituitary of vertebrates. They are central to the complex endocrine system that regulates normal growth, sexual development, and reproductive function. The hormone family includes the mammalian hormones follicle-stimulating hormone (FSH) and luteinizing hormone (LH), the placental/chorionic gonadotropins, human chorionic gonadotropin (hCG) and equine chorionic gonadotropin (eCG), as well as at least two forms of fish gonadotropins. LH and FSH are secreted by the anterior pituitary gland, while hCG and eCG are secreted by the placenta in pregnant women and mares, respectively. The gonadotropins act on the gonads, controlling gamete and sex hormone production. Gonadotropin is sometimes abbreviated Gn. The alternative spelling gonadotrophin which inaccurately implies a nourishing mechanism is also used. There are various preparations of gonadotropins for therapeutic use, mainly as fertility medication. There are also fad diet or quack preparations, which are illegal in various countries.

Natural types and subunit structure The two principal gonadotropins in vertebrates are luteinizing hormone (LH) and follicle-stimulating hormone (FSH), although primates produce a third gonadotropin called chorionic gonadotropin (CG). LH and FSH are heterodimers consisting of two peptide chains, an alpha chain and a beta chain. LH and FSH share nearly identical alpha chains (about 100 amino acids long), whereas the beta chain provides specificity for receptor interactions. These subunits are heavily modified by glycosylation. The alpha subunit is common to each protein dimer (well conserved within species, but differing between them), and a unique beta subunit confers biological specificity. The alpha chains are highly conserved proteins of about 100 amino acid residues which contain ten conserved cysteines all involved in disulfide bonds, as shown in the following schematic representation.

+---------------------------+ +----------+| +-------------|--+ | || | | | xxxxCxCxxxxxxCxCCxxxxxxxxxxxxxCCxxxxxxxxxxCxCxxCx | | | | +------|-----------------+ | | | +----------------------------+

'C': conserved cysteine involved in a disulphide bond. Intracellular levels of free alpha subunits are greater than those of the mature glycoprotein, implying that hormone assembly is limited by the appearance of the specific beta subunits, and hence that synthesis of alpha and beta is independently regulated. Another human gonadotropin is human chorionic gonadotropin (hCG), produced by the placenta during pregnancy.

Mechanism

Gonadotropin receptors are embedded in the surface of the target cell membranes and coupled to the G-protein system. Signals triggered by binding to the receptor are relayed within the cells by the cyclic AMP second messenger system. Gonadotropins are released under the control of gonadotropin-releasing hormone (GnRH) from the arcuate nucleus and preoptic area of the hypothalamus. The gonads — testes and ovaries — are the primary target organs for LH and FSH. The gonadotropins affect multiple cell types and elicit multiple responses from the target organs. As a simplified generalization, LH stimulates the Leydig cells of the testes and the theca cells of the ovaries to produce testosterone (and indirectly estradiol), whereas FSH stimulates the spermatogenic tissue of the testes and the granulosa cells of ovarian follicles, as well as stimulating production of estrogen by the ovaries. Although gonadotropins are secreted in a pulsatile manner (as a result of pulsatile GnRH release), unlike the case of GnRH and GnRH agonists, constant/non-pulsatile activation of the gonadotropin receptors by the gonadotropins does not produce functional inhibition. This can be seen during the first 7–10 weeks of pregnancy, where constantly high and progressively-increasing levels of hCG circulate and mediate production of estrogen and progesterone by the corpus luteum until the placenta takes over the production of these hormones.

Diseases Gonadotropin deficiency due to pituitary disease results in hypogonadism, which can lead to infertility. Treatment includes administered gonadotropins, which, therefore, work as fertility medication. Such can either be produced by extraction and purification from urine or be produced by recombinant DNA. Failure or loss of the gonads usually results in elevated levels of LH and FSH in the blood. LH insensitivity, which results in Leydig cell hypoplasia in males, and FSH insensitivity, are conditions of insensitivity to LH and FSH, respectively, caused by loss-of-function mutations in their respective signaling receptors. Another closely related condition to these is GnRH insensitivity.

Pharmaceutical preparations

There are various preparations of gonadotropins for therapeutic use, mainly as fertility medication. For example, the so-called menotropins (also called human menopausal gonadotropins) consist of LH and FSH extracted from the urine of menopausal women. There are also recombinant variants. Besides the aforementioned legitimate pharmaceutical drugs, there are fad diet or quack preparations, which are illegal in various countries.

See also Antigonadotropin Gonadotropin surge-attenuating factor

References

External links Gonadotropins at the U.S. National Library of Medicine Medical Subject Headings (MeSH) 10th International Symposium on GnRH

Worked examples

Example 1 — a first encounter with Gonadotropin

Start with the simplest possible case. Write down what Gonadotropin claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Gonadotropin before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Gonadotropin ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Gonadotropin

In research: Gonadotropin appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Gonadotropin in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Gonadotropin is common in secondary-school and first-year university syllabi. It links to neighbouring topics Animal reproductive system, Gonadotropin-releasing hormone and gonadotropins, Hormones of the hypothalamus-pituitary-gonad axis, so understanding it makes those chapters shorter.
In everyday life: Look for Gonadotropin outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Gonadotropin in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Gonadotropin means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Gonadotropin out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Gonadotropin in simple terms?

Why does Gonadotropin matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Gonadotropin?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Gonadotropin.