KNES 355 Final Exam Review Part 1

sex determination and endocrine system

At week ____ since fertilization, the embryo has both male and female primordial genital ducts (internal genitalia), meaning it has ____________.

7, bipotential

What are DSD’s?

differences in sex development

a mismatch between chromosomal sex (XX or XY) and anatomical sex

What is Klinefelter (47XXY) syndrome?

• genetically male XY has an additional copy of X chromosome

• sex chromosome abnormality (too many), causing feminization:

  • tall + lean

  • long arms + legs

  • broad hips

  • female pattern of pubic hair

  • breast development

• one of the most common chromosomal disorders (1/1000)

What is the cause of Klinefelter?

non-disjunction event during maternal or paternal meiosis I or II

What is Turner (45X) syndrome?

• missing sex chromosome

  • non-disjunction event

• appears female, but has different somatic growth + reproductive function

  • short stature

  • underdeveloped, non-functional ovaries

  • internal/external genitalia appear normal

  • infertility + primary amenorrhea (no menstruation)

  • lack of secondary sex characteristics

What is androgen insensitivity (46XY)?

• genetically male (XY) but deficient in androgen receptors in target tissues (penis, testes)

  • spectrum of sex phenotypes

• phenotype influenced by mutation on X chromosome

• mostly female external sex characteristics

  • can’t respond to androgens

  • undescended testes

  • no uterus

What is 5 alpha reductase enzyme deficiency (46XY)?

• specific gene mutation on a non-sex chromosome-influencing sex phenotype

• genetic autosomal origin resulting in target tissue deficiency in the production of an enzyme required for converting androgen precursors to testosterone

• not a receptor problem, but a gene end-product deficiency

How does a 5 alpha reductase enzyme deficiency present?

• genetic male (XY)

• female external genitalia appearance pre-puberty, or ambiguous

• may develop some male secondary sex characteristics during puberty

What factors contribute to human phenotype variation?

• genetic effects

• environmental effects (intra + extra-uterine)

• gene-environment interaction

What part of the brain controls the endocrine system?

hypothalamus

How many hormones does the anterior pituitary release? What are they?

6 primary hormones:

• GH

• TSH

• ACTH

• PRL

• FSH

• LH

What is the difference between a tropic hormone and a non-tropic hormone?

tropic: targets other endocrine glands to release other hormones

non-tropic: act directly on target tissues/cells

Of the 6 hormones released by the anterior pituitary gland, which is(are) non-tropic?

prolactin

What happens in the follicular phase of the menstrual cycle?

• estrogen + progesterone are low (menstruation occurs)

• anterior pituitary increases FSH production (stimulates growth of follicles)

• follicles produce estrogen (stimulates LH)

• LH surges, causing follicle to rupture + egg to be released (ovulation)

What occurs in the luteal phase (after ovulation)?

• ruptured follicle closes after releasing egg (corpus luteum)

  • produces progesterone

• prepares uterus for implantation of embryo

• if egg isn’t fertilized or doesn’t implant, corpus luteum degenerates after 14 days

  • progesterone decreases + new menstrual cycle begins

Fill in the blanks for the sequence of events of the menstrual cycle:

1. GnRH from the hypothalamus stimulates the ______________ gland to release ________.

2. _______ stimulates growth of follicles.

3. Follicles produce __________.

4. ___________ stimulates the hypothalamus/anterior pituitary to release surge of _____.

5. _____ surge causes follicles to rupture.

6. Corpus luteum produces ________________.

1. anterior pituitary. FSH

2. FSH

3. estrogen

4. Estrogen, LH

5. LH

6. progesterone

How does the hypothalamus-pituitary-growth axis regulate growth?

• direct action (anabolic)

• tropic (targets other glands)

What is the direct action of the hypothalamus-pituitary-growth axis?

• growth of all tissues in the body

• GH levels rise during childhood, peak during puberty

• regulated by GHRH produced by the hypothalamus

What is the tropic action of the hypothalamus-pituitary-growth axis?

• growth hormone stimulates liver to produce insulin-like growth factor (IGF-1)

• IGF-1 stimulates growth in many body tissues

Growth hormone is a _____________ hormone, meaning it is highest in the first 2 hours of sleep.

nocturnal

IGF-1 gene mutations disrupt _____________ and _____________ growth.

in utero, postnatal

Growth hormone mutations primarily disrupt ________________ growth.

postnatal

During puberty, ____________________ promote growth hormone secretion.

sex hormones

At puberty, the hypothalamus increases production of __________________, which triggers the release of ______ and ______ from the anterior pituitary.

gonadotropin releasing hormone (GnRH), LH, FSH

The hypothalamus-pituitary-gonadal (HPG) axis has a _________________ to the pituitary and hypothalamus, telling them to stop production of _________ and _________.

negative feedback loop, FSH, LH

FSH stimulates ________________, LH stimulates ___________ in the testes, which produce ______________.

spermatogenesis, the Leydig cells, testosterone

In spermatogenesis, ____________ spermatogonia differentiate into ______________ spermatozoa.

diploid, haploid

What is the adrenal axis (HPA) responsible for?

• pre-pubertal increases in fat in both sexes

• secondary sex characteristics (pubic hair + facial hair)

What hormones are involved in the HPA?

corticotropin RH (from the hypothalamus)

adrenocorticotropic hormone (ACTH) (from the pituitary)

DHEA + DHEAS (increase sweat + oil production in skin, activate growth of body hair)

What is adrenarche?

awakening of adrenal glands

When does adrenal activation occur? What occurs?

5-8 yrs old

• development + maturation of adrenal cortex

• increased secretion of DHEA and DHEA-S (adrenal pro-hormones), plus small amounts of sex steroids (estrogen + testosterone)

• adrenal pro-hormones converted to sex steroid hormones in the presence of the enzyme aromatase in most somatic tissues

Peak growth hormone coincides with ______________.

peak growth velocity

_____________ and _____________ are predominant during childhood, whereas _____________ is predominant during adolescence, along with the other two.

Growth hormone, IGF-1, gonadal sex steroids (estrogen, progesterone, testosterone)

What is the pubertal timing for boys and girls?

boys: rarely before 9 years of age, late if no signs by 14 years

girls: rarely before 8 years of age, usually by 13 years, late if no thelarche (breast budding) by 13 years or amenorrheic after 15 years