Brief Answer:
The answer is yes to both your questions.

Detailed Answer:
Hi,

Welcome to Healthcare Magic!

Your first question is regarding puberty. Yes, the increase in gonadotrophin secretion in puberty is mirrored in the preceding Gonadotrophin releasing hormone secretion (GnRH) also. First the GnRH secretion from the hypothalamus increases and then only the gonadotrophin secretion increases. The secretion of both GnRH and gonadotrophin hormones is pulsatile. The cause of increase in GnRH secretion at puberty is not known, but leptin hormone has been implicated.

When the GnRH from the hypothalamus reaches the pituitary gland, it stimulates the secretion of gonadotrophins. This process is controlled by two main factors:
1) Amplitude and frequency of GnRH pulses
2) Negative feedback from androgens and estrogen present in the body

Regarding your second question, exogenous androgens /anabolic steroids suppress both GnRH secretion from hypothalamus and gonadotrophin secretion at the pituitary. Exogenous androgens directly affect the activity of the GnRH pulse generator. Effect of exogenous androgens on gonadotrophin secretion is both direct and also secondary to the effect on GnRH secretion. The effect is so strong that people have studied if exogenous testosterone can be used as a male contraceptive or not.

Hope this answers your query. Please feel free to ask if you want any clarifications.

Best wishes.

Dr Preeti Parakh,
MD Psychiatry

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Brief Answer:
No, androgens do not affect pubertal GnRH pulse.

Detailed Answer:
Hi,

Thanks for writing back!

During puberty, adrenal glands secrete androgens like dehydroepiandrosterone even before the GnRH pulse generator becomes active. These androgens are responsible for development of pubic hair and some other pubertal changes. However, they have no role in activation of GnRH pulse generator. Once GnRH pulse generator becomes active, the gonads start producing testosterone or estrogen and rest of the pubertal changes occur. The gonadal hormones provide negative feed back to the GnRH pulse generator.

Hope this answers your query.

Best wishes.

Dr Preeti Parakh
MD Psychiatry

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Brief Answer:
Yes, you are right.

Detailed Answer:
Hi Rony,

Thanks for writing back!

Yes, you are right. Some changes take place in the brain at puberty which increase the activity of the GnRH pulse generator. While the exact mechanism is not yet known, the following have been implicated.

1)Kisspeptins

In just the past few years, kisspeptins have emerged as a critical component of the system that controls the level of GnRH neuronal activity between infancy and puberty. Kisspeptins are neuropeptides and hypothalamic kisspeptin secretion is distinctly pulsatile and highly correlated with that of GnRH.

2) Leptin

Leptin is produced by adipocyte and has been implicated as one way in which metabolic signals might be communicated to the higher centers controlling the activity of the hypothalamic pulse generator at the onset of puberty. Leptin-deficient mice and rats fail to enter puberty, and treatment with leptin induces the onset of puberty. Similarly, children with malnutrition have delayed puberty probably because of this.

3) Glutamate

Glutamate is an excitatory neurotransmitter in the hypothalamus and has been shown to stimulate GnRH release in experiments.

4) Gamma-aminobutyric acid (GABA)

Gamma-aminobutyric acid (GABA) is an inhibitory neurotransmitter produced by specialized neurons in the hypothalamus and has an important role in regulating the activity of the GnRH pulse generator. It acts as a "neurobiologic brake" to restrict GnRH secretion till puberty occurs.

5) Neuropeptide Y (NPY)

Neuropeptide Y is a hypothalamic peptide involved in the control of food intake behavior and reproductive function in adults. It has been suggested that NPY, like GABA, is an important component of the “neurobiologic brake” that restrains the GnRH pulse generator in prepubertal age.

It is believed that these chemicals interact with each other and together are responsible for the increase of pulsatile GnRH secretion at the onset of puberty.

Hope this answers your query. Please feel free to ask if you need any other clarifications. I shall try to answer to the best of my capability. But if there are no more queries, then please close the discussion and rate it.

Best wishes.

Dr Preeti Parakh
MD Psychiatry

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