Puberty and Male Development Quiz

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Questions and Answers

Which gland enlarges and begins to secrete fructose during male development?

Bulbourethral gland

Leydig cells

Seminal vesicles (correct)

Prostate gland

What effect does testosterone have on the voice during puberty?

Larynx enlarges and vocal cords increase in length (correct)

Voice remains unchanged

Voice becomes higher in pitch

Vocal cords shorten

Which of the following describes the pattern of pubic hair growth in males during puberty?

Random scattering

Circle shape

Triangle with apex up (correct)

Horizontal lines

What is the primary action of DHT-receptor complexes during puberty?

Enlarge external genitalia and stimulate hair growth Signup and view all the answers

Which of the following is NOT an effect of increased testosterone production?

Reduced muscle mass Signup and view all the answers

What happens to the skin due to testosterone's effects during puberty?

Thicker sebaceous gland secretion Signup and view all the answers

What is the primary source of estrogens in adult men?

Aromatization of testosterone and androstenedione Signup and view all the answers

What is one of the anabolic effects of testosterone?

Increased synthesis and decreased breakdown of protein Signup and view all the answers

What is the main site of testosterone secretion?

Leydig cells Signup and view all the answers

What percentage of testosterone in plasma is bound to sex steroid-binding globulin (GBG)?

65% Signup and view all the answers

Which hormone stimulates the synthesis of testosterone in Leydig cells?

Luteinizing hormone (LH) Signup and view all the answers

Most of the testosterone in plasma is converted to which hormone?

Androsterone Signup and view all the answers

Which of the following is an isoform of the progesterone receptor?

PRB Signup and view all the answers

What is the main site of metabolism and excretion of oestrogens?

Liver Signup and view all the answers

Which feature is NOT associated with female secondary sex characteristics due to oestrogens?

Increased body hair Signup and view all the answers

What is the primary method by which testosterone production is regulated?

Adenylate cyclase activation via Gs protein Signup and view all the answers

How does oestrogen affect the cervical mucus?

Makes it thinner and more alkaline Signup and view all the answers

Which of the following hormones exhibits episodic secretion during the follicular stage of the menstrual cycle?

Follicle-stimulating hormone (FSH) Signup and view all the answers

What is the role of pulsatile secretion of gonadotropin-releasing hormone (GnRH)?

Regulating reproduction Signup and view all the answers

What effect does oestrogen have on the uterine muscle?

Increases sensitivity to oxytocin Signup and view all the answers

What is the purpose of the transformation of oestrogens into glucuronide and sulfate conjugates?

To facilitate their excretion Signup and view all the answers

During which phase of the menstrual cycle does oestrogen primarily promote endometrial proliferation?

Follicular phase Signup and view all the answers

What happens to the vaginal epithelium under the influence of oestrogen?

It undergoes cornification Signup and view all the answers

Which effect is indicative of oestrogen's role in breast development?

Proliferation of mammary ducts Signup and view all the answers

What role do Sertoli cells play in spermatogenesis?

They secrete ABP to maintain local testosterone concentration. Signup and view all the answers

What effect does systemically administered testosterone have on LH secretion?

It inhibits LH secretion. Signup and view all the answers

Which statement accurately describes the stability of testosterone-receptor complexes compared to DHT-receptor complexes?

DHT-receptor complexes are more stable. Signup and view all the answers

Which type of hypogonadism is characterized by high LH levels but low testosterone levels?

Hypergonadotropic hypogonadism Signup and view all the answers

What is one of the psychological effects of male hypogonadism?

Loss of libido Signup and view all the answers

Which enzyme is responsible for converting testosterone to DHT?

5α-reductase Signup and view all the answers

What is one potential physical characteristic of adolescents with hypogonadism from childhood?

Eunuchoid tall stature Signup and view all the answers

What is the primary symptom of androgen-secreting Leydig cell tumors in prepubertal boys?

Precocious pseudopuberty Signup and view all the answers

How does congenital 5α-reductase deficiency affect individuals at puberty?

They develop male body contours and libido Signup and view all the answers

How does testosterone affect spermatogenesis in the context of its systemic administration?

It decreases sperm count by inhibiting LH secretion. Signup and view all the answers

Which of the following statements about dihydrotestosterone (DHT) is correct?

DHT binds more effectively to the same receptor as testosterone Signup and view all the answers

What triggers the enlarging of the clitoris in individuals with congenital 5α-reductase deficiency during puberty?

High luteinizing hormone and testosterone production Signup and view all the answers

Which hormone functions to inhibit FSH secretion in both men and women?

Inhibin B Signup and view all the answers

Which hormone can inhibit LH secretion at normal physiological levels?

Inhibin Signup and view all the answers

What stimulates the secretion of FSH?

Activins Signup and view all the answers

Where are inhibins predominantly produced in males?

Sertoli cells Signup and view all the answers

What is the primary clinical use of finasteride?

To treat benign prostatic hyperplasia Signup and view all the answers

What generally occurs to individuals with congenital 5α-reductase deficiency at puberty?

They develop male secondary sexual characteristics Signup and view all the answers

What is one of the roles of relaxin during pregnancy?

Facilitating delivery Signup and view all the answers

Which inhibin specifically regulates FSH secretion in men?

Inhibin B Signup and view all the answers

Which of these conditions is associated with androgen dependency?

Prostate carcinoma Signup and view all the answers

Which substance is found in semen and may help maintain sperm motility?

Relaxin Signup and view all the answers

Which hormone is known to inhibit uterine contractions during pregnancy?

Relaxin Signup and view all the answers

What is the primary function of inhibins in the pituitary gland?

Inhibiting FSH secretion Signup and view all the answers

Study Notes

Reproductive Hormones

Reproductive hormones affect all aspects of reproductive function, including growth during puberty and aging.
Outcomes include outlining the synthesis, metabolism, regulation of secretion of sex hormones.
Describing the mechanism of actions and effects of sex hormones during puberty and in adults.
Describing the hormonal basis of ovular and anovular menstrual cycles and signs of ovulation.
Discussing the manipulation of menstrual cycles (e.g., contraceptives).
Describing the effects of 5α-reductase deficiency, orchidectomy (before and after puberty), and congenital adrenal hyperplasia.

Synthesis: Estrogens

Cholesterol is the basic ingredient for all steroid hormones.
Estrogens (estradiol, estrone, estriol) are synthesized in the ovaries.
The process involves several enzymatic steps, starting with cholesterol, transforming into pregnenolone and other intermediates.
Aromatase is a key enzyme converting androstenedione into estrogens.
Theca cells produce androgens, and further converted to estrogens by granulosa cells.
Estrogens circulate in the blood.

Metabolism and excretion

The primary site for metabolism is the liver.
Estrogens are converted to glucuronide and sulfate conjugates.
Metabolites and conjugates are subsequently excreted in the urine.
Some amounts are secreted in the bile and reabsorbed into the bloodstream (enterohepatic circulation).

Actions of Estrogens

Estrogens lead to the development of secondary sex characteristics in women.
These include changes in body proportions (wide hips, narrow shoulders), distribution of fat deposits (breasts, buttocks), development of the larynx retaining its prepubertal proportions (high-pitched voice).
Estrogens also contribute to the growth of pubic and axillary hair.
Estrogens affect the female reproductive tract; proliferation of endometrium, uterine glands lengthen, makes cervical mucus thinner and more alkaline to promote sperm survival and transport.
Cervical mucus has a fern-like pattern. Vaginal epithelium becomes cornified.
Other impacts include the proliferation of mammary ducts, facilitate the growth of ovarian follicles, and increase the motility of uterine tubes, and increase uterine blood flow.
These influence the content of contractile proteins in uterine muscle and sensitizes the uterus to oxytocin.
Estrogens also contribute to bone density, blood cholesterol levels.

Synthesis: Progesterone

Progesterone is synthesized from cholesterol, via pregnenolone as an intermediate.
The synthesis mainly occurs in the corpus luteum and placenta during pregnancy.
Progesterone is crucial for maintaining pregnancy.
Progesterone influences the uterus and affects the endometrium, breasts, and brain, thus influencing female behavior patterns.

Secretion, Transport and Metabolism: Progesterone

Secretion sites include the corpus luteum, placenta and in small amounts the follicle; 80% bound to albumin and 18% to corticosteroid binding globulin.
The main target organs are uterus, breasts, and brain.
Progesterone influences endometrium to maintain the secretory phase, increases uterine glands tortuosity, spiral arteries tortuosity, and secretion of glands.
Thickens cervical mucus and inhibits the ferning caused by estrogen.
The epithelium proliferates and becomes infiltrated with leukocytes (vagina).

Effects of Progesterone

Antiestrogen effect, decreasing myometrial excitability, sensitivity to oxytocin, and spontaneous electrical activity.
Decreases estrogen receptors in endometrium and increases conversion of estrogen to less active forms.
Growth of lobules and alveoli in the breast.
Large doses of progesterone inhibit LH secretion and potentiate the effects of estrogen, thus preventing ovulation.
Progesterone is thermogenic, potentially influencing the rise in basal body temperature during ovulation.
Prominent in respiratory and alveolar PCO2 regulation during pregnancy.

Mechanism of actions

Estrogen receptors (ERα and ERβ), primarily with genomic effects, but also some rapid non-genomic effects.
Progesterone works via action on DNA, new mRNA synthesis. Progesterone receptor binds to a heat shock protein in the absence of progesterone.
Progesterone binding releases the heat shock protein, unveiling the DNA-binding domain of the receptor.
Two isoforms of the progesterone receptor exist: PRA and PRB.

Regulation or Ovarian Hormone Secretion

Regulation of ovarian secretion depends on the hypothalamic-pituitary-gonadal (HPG) axis.
GnRH from the hypothalamus stimulates the anterior pituitary to release LH and FSH.
Ovaries produce inhibin B to negatively regulate FSH release.
Estrogen and progesterone have negative feedback loops to regulate LH and FSH.
These regulatory mechanisms control the menstrual cycle.

Synthesis of Male Reproductive Hormones

Testosterone is the principle hormone synthesized in the testes, from cholesterol via intermediates such as pregnenolone, progesterone and others.
The location of synthesis is primarily Leydig cells.
Androstenedione is another source of testosterone.
In some target tissues, androstenedione is converted to dihydrotestosterone.

Metabolism

Most (98%) of testosterone in the plasma is bound to a protein.
65% bound to gonadal steroid- binding globulin (GBG), 33% to albumin.
A small amount of testosterone converts to estradiol.
Most testosterone converts to androsterone and excreted in the urine.

Actions of Testosterone

Testosterone regulates functions of the testes and, through the androgen receptor, exerts effects on a wide range of target cells.
These actions include spermatogenesis, development of secondary sexual characteristics, sexual differentiation, growth of reproductive organs, and libido.
Dihydrotestosterone (DHT) amplification occurs in some target cells.

Actions: Secondary Sex Characteristics

Testosterone affects external genitalia (penis growth, scrotum pigmentation).
Internal genitalia (enlargement of seminal vesicles, prostate, and bulbourethral glands).
Voice changes (larynx enlargement, deeper voice).
Hair growth (beard, pubic, axillary hair).
Mental functions (increased aggression, activity, interest in opposite sex).
Body conformation (shoulders broaden, muscles enlarge).
Skin (sebaceous gland secretion increases, predisposing to acne).

Effects on Hairline

Testosterone affects hair growth and loss patterns.

Actions: Anabolic Effects

Testosterone increases protein synthesis and decreases breakdown. Increases rate of growth.
Moderate Na+, K+, H2O, Ca2+, SO4²⁻, and PO₄³⁻ retention.
Kidney size may be increased.
Exogenous testosterone can increase libido but may present masculinizing, and limits usefulness in wasting diseases.
Most estrogens in adult men are produced by extragonadal tissue or adrenal glands, not directly from the testes.

Spermatogenesis

Sufficient testosterone concentration is needed to maintain spermatogenesis in seminiferous tubules.
Sertoli cells produce androgen-binding protein (ABP) to maintain a high local concentration of testosterone.
Testosterone readily diffuses through Leydig, Sertoli cells and blood testes barrier.

Regulation

Systemically administered testosterone does not increase androgen levels.
Inhibition of LH secretion leads to decreased testosterone synthesis and decreased sperm count.

Mechanism

Testosterone binds to an intracellular androgen receptor (NR3C4).
Receptor complex binds to DNA, facilitates transcription of genes.
Testosterone can be converted to DHT 5α-reductase, in some target cells.
DHT binds to the same intracellular receptor.
DHT-receptor complexes are more stable than testosterone-receptor complexes.

Abnormalities of Testicular Function

Cryptorchidism: Undescended testes.
Male Hypogonadism classifications are:
- Hypergonadotropic (High LH, low testosterone: testicular failure).
- Hypogonadotropic (Low testosterone, normal or low LH).
Long Term Effects: Loss of libido with related symptoms.
Adolescent effects are usually permanent, tall, narrow shoulders, small muscles, a body configuration resembling the female.
- High-pitched voice, sparse hair.

Congenital 5α-Reductase Deficiency

Genetic mutation of 5α-reductase 2 gene.
Male internal genitalia (testes) but female external genitalia.
At puberty, LH secretion and circulating testosterone increase.
Develop male body contours, libido increases.
Clitoris enlargement ("penis-at-12 syndrome") enough testosterone may overcome need for DHT.
Prostatic hyperplasia treatment includes 5α-Reductase inhibiting drugs.

Other Hormones

Relaxin is a polypeptide hormone.
Present in the corpus luteum, uterus, placenta, mammary glands (in women), and prostate (in men).
It facilitates delivery during pregnancy by relaxing pubic symphysis and other pelvic joints.
It also inhibits uterine contractions, and plays a role in mammary gland development.
Found in non-pregnant women in corpus Luteum and endometrium during secretory phase; and in semen, aiding motility/penetration of ovum.
Inhibins are produced by Sertoli cells (males) and granulosa cells (females).
Inhibits FSH secretion.
Activins stimulate FSH secretion, but their role is unclear.

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Description

Test your knowledge on male puberty and development with this quiz. Questions cover the role of various hormones, changes in the body, and the physiological processes involved. Understand the intricate details of how testosterone and related substances affect males during adolescence.